because if you don't move your mouse often your computer goes to sleep to save power or because you have a bad computer and minecraft costs too much CPU [proccesor] usage so your computer goes to screen saver to prevent burning
no you can not
You can play Minecraft from as many computers as you want as long as you log in on each one from your account.
Minecraft is all about the account you made, you can log into that account on any computer, you are not forced to play it only on the computer that you purchased it on.
Play the game
Yeppers.
Yes, simply download it from the minecraft website.
obviously its amazing for ur computer if u play minecraft ur the best! :D
you just have to download it on the computer you want that minecraft to be
Yes, actually minecraft first came out on computer
Yes you can, but you need to download minecraft for macs
No
if it is a computer