1. I saw this creature that had the ability to untap itself the player used this ability to attack several times in one turn, is that legal, or does your turn end the first time you attack?
2. What happens when you unsummon a creature token?
What is "the stack?"
During each players turn, they get only one attack phase. This means, during their mainphase, they may declare an attack step, only at which time may creatures attack. A creature may only attack once each turn unless the player is given another attack step (Relentless Assualt, Seize the Day).
If a creature token leaves play for any reason, it is removed from the game. That includes unsummon effects, destruction, and any other effect that removes it from play.
The short explanation is that the stack is a sort of limbo place where spells and abilities go while they are waiting to resolve. Each time something happens in the game (other than playing a land or generating mana) that action goes on the stack, where it waits to see if any player wants to respopnd to it.
When neither player wants to respond with any more actions, the top (last played) spell or ability on the stack resolves. Then, if both players still opt not to do anything, the next thing will resolve, etc.
Alright I think I get it:
Bob has a wind drake out and Joe has an Obsidian Acolyte and a Razorfoot Griffin.
Bob casts Terror to kill the Razorfoot Griffin.
Joe's Obsidian Acolyte uses its ability to give Razorfoot Griffin Protection from black.
Because Joe used this ability after the Griffin will be saved.
Last in, first out.
So, yes, Madman, you are correct.