Is playing minecraft for 4 hours a day healthy?

If you're doing something productive in that time in the game, sure. I mean, there's a difference between a kid and adult playing a game that simple so long. I would expect an adult to be at least trying to construct some dreamt up masterpiece or at least a server. If not, they might as well play a game where they can actually learn something. (You can learn how to make servers and what not in Minecraft, but not while actively playing it. ).

And on the non - hypothetical health side, I don't see why not unless you have other health issues that would interfere such as epilepsy.

Nope

In general no.
However if you take little breaks every 30 minutes or so to relax your eyes and do something else, like do some homework, then you'll last a little longer and you will probably have a less chance of getting a headache.
Breaks are your friend!

Is playing fallout 3 for 17 hours straight good? Because i think thats my current record

I also think No.

Its hard to believe i'm not the one that sent in this question lol

Of course not!