This is an older blog fad that passed through a few years ago. Naturally, I just discovered it, and naturally, I don't care how old it is, I'm going to answer them anyway. This is, perhaps, an interesting Rorschach test for gaming tastes and preferences overall.
The First Set
1). Race (Elf, Dwarf, Halfling) as a class? Yes or no? I don't really care. I tend to prefer no, but it's not a strong preference. Part of this was Gary Gygax's own inability to come to terms with the idea that players might want to play anything other than human. As I've aged, or my tastes have evolved, or whatever you want to call it, I've come more into sympathy with this perspective. So I don't have any problem with what earlier seemed like bizarrely arbitrary rules like the race as class stuff (and #4 below too.)
2). Do demi-humans have souls? I have never once attempted to answer this question. I know it's a permutation of the raise dead spell and some fluff around it, but I've never given it any thought. I prefer that there be no raise dead spell at all, personally, and if there is, I prefer not to think through the metaphysical questions that it begs anyway.
3). Ascending or descending armor class? Ascending. Descending is a bizarre artifact of older games. And I never played enough D&D to ever really memorize the THAC0 table. But again; not something that I care a lot about as a player. As a GM, my preference is more strongly towards ascending.
4). Demi-human level limits? Sure, why not. Honestly, moot point. My own personal preference is for campaign level limits that are below the lowest of the demi-human level limits anyway.
5). Should thief be a class? Yes, absolutely. It's one of my favorite classes to play.
6). Do characters get non-weapon skills? Yes, absolutely. I strongly disagree with the received OSR wisdom that skills "ruined" the "I can do anything I want" paradigm of the game prior to their existence. That's only true for profoundly stupid players—or at least players and GMs that lacked initiative and didn't believe in rulings.
7). Are magic-users more powerful than fighters (and, if yes, what level do they take the lead)? I have no preference. I will point out that in the sword & sorcery literature, magic-users tend to be played as if they are really powerful. That said, fighters (like Conan, for instance) seem to routinely be able to deal with them. Conan is, of course, exceptional. But then, so are all PCs, right?
8). Do you use alignment languages? No. I don't even use alignments.
9). XP for gold, or XP for objectives (thieves disarming traps, etc...)? Get rid of XP altogether. Advancement to a new level is the purview of GM ruling. This actually is a rule that I think would have been better off unstated and left in the GM's hands. It's curious that OSRians complain so bitterly about skill systems taking rulings out of the hands of GMs (which isn't actually true) but they are often extraordinarily strict about how they think XP should be deployed. I dislike XP altogether and prefer to toss the whole system.
10). Which is the best edition; ODD, Holmes, Moldvay, Mentzer, Rules Cyclopedia, 1E ADD, 2E ADD, 3E DD, 4E DD, Next ? I'd play Moldvay for quite a while. Eventually I'd get annoyed with its idiosyncrasies, but it'd take a while. I'd play 3e, but only if it were contained within a fairly narrow window (I think the system is absolutely atrocious for the top two thirds of the levels presented.) And curiously, even though it was designed to be foolproof from a DMing perspective, I think it requires more than most other systems a really good DM to be fun to play. Either that or I just don't think the designers are good DMs and I disagree with them fundamentally on the nature of how to DM. And finally, I'd play 5e just to try it out, I suppose, if someone else were to offer to run it. That doesn't make it in the running for the "best" edition, but in reality, those are the only three that I'd even be willing to play at all.
Bonus Question: Unified XP level tables or individual XP level tables for each class? Don't have a strong opinion either way. Don't care. Surprising to me that I actually don't care a lot about more of these questions than I thought; but in most of them, even though I didn't care very much, I at least had a weak preference. In this one, I honestly have no preference whatsoever.
The Second Set
1). Should energy drain take away one level of experience points from the character? Yes or No? If no, what should level drain do? No, that's complicated to do, and kinda finicky and metagamey anyway. I'd prefer to do away with energy drain entirely and replace it with CON drain everywhere where it appears.
2). Should the oil used in lanterns do significant damage (more than 1 hp in damage) if thrown on an opponent and set on fire? Yes or No? If yes, how much damage should it do? Depends. Is the assumption that it's difficult to put out the fire, or that it clings, or whatever? If a character so attacked can immediately "stop, drop and roll" (reflex save once hit?) I'd rule that no, it doesn't do significant damage really—although it'd sure screw you up tactically for a round or two. Otherwise, sure—being set on fire sucks. That's why being burned at the stake was a fatal sentence, after all. 1d6 per round until put out or character dies.
3). Should poison give a save or die roll, with a fail rolled indicating instant death? Yes or No? If no, how should game mechanics relating to poison work? Depends on the poison. I don't have a problem with that in general. I don't think that applies to every poison. Plenty of poisons are not immediately fatal. Plenty of poisons aren't fatal at all. I like the d20 use of poison, actually. It made a lot of sense to me. although I don't like long lists of poisons. I like "Schrödinger's poison" with effects that you make up on the fly. CON damage, or become violently ill, or whatever.
4). Do characters die when they reach 0 hit points? Yes or No? If no, then at what point is a character dead? I tend to go to negative CON, but I don't feel strongly about it, and I'm coming around more and more to 0 = dead. Right now, I'm settling on a 0 = make a saving throw or die immediately. Make this throw every round until character is either stabilized, healed, or dies. I guess that kinda splits the difference, right?
5). Does the primary spell mechanic for a magic user consist of a "memorize and forget system" (aka Vancian)? Yes or No? If no, what alternative do you use? I use m20, which uses a "casting spells causes HP damage" mechanic. I like it, especially when coupled with a lightweight sanity system which is also damaged by casting spells. Instead of Vancian, I prefer to call this system "Lovecraftian."
6). Should all weapons do 1d6 damage or should different weapons have varying dice (1d4, 1d8, etc...) for damage? I prefer various weapon damages, but I think that the standard array of weapon damages that is common to D&D and D&D derived games probably leaves a lot to be desired. I've never bothered trying to change it significantly, though.
7). Should a character that has a high ability score in their prime requisite receive an experience point bonus? Yes or No? No, but see above. Get rid of XP. That was a poorly conceived idea from the get-go anyway.
8). Should a character with an constitution of 18 get a +3 bonus to hit points, or a +2 bonus to hit points, or a +1 bonus to hit points or no bonus to hit points? And should other ability scores grant similar bonuses to other game mechanics? No to all. Having a high ability score is a good enough benefit in its own right.
9). Should a character have 1 unified saving throw number, or 3 saving throw types based on ability scores (reflex, fortitude, will), or 5 types based on potential game effects (magic wand, poison attacks)? or something else? I like how m20 has folded saving throws into the skill system (such as it is.) Saving throws themselves are an odd mechanic that stands out oddly. I also think it strange that saving throws correspond to an ability so closely; in that case, why not just use an ability check in place of the saving throw (I know, I know; because we want to scale saving throws with level. Or at least the designers did.) I'm actually not a fan of the saving throw mechanic at all, honestly. Especially not in earlier games where they were bizarre and arbitrary; save against breath weapon, save against poison, etc. Third edition made saving throws more logical, but they also, ironically, made them superfluous.
To some degree that edition did the same to ability scores, but that's a whole 'nother question.
10). Should a cleric get (A) 1 spell at 1st level (B) no spells at 1st level (C) more than 1 spell at 1st level? The cleric class should be removed from the game entirely. The Thief archetype has much more standing, especially as based on the source literature, than the cleric does.