Yes, in Magic: The Gathering, you tap your creatures to block attacking creatures during combat.
Yes, in Magic: The Gathering, you tap your creatures to indicate that they are blocking an attacking creature.
Yes, in a game of Magic: The Gathering, you have to tap a creature to use it to block an attacking creature.
Yes, tap abilities are instant in Magic: The Gathering.
Yes, when a creature is assigned to block an attacking creature in a game of Magic: The Gathering, it does tap as part of the blocking process.
Yes, tap abilities are considered activated abilities in Magic: The Gathering.
No, you cannot use tap abilities in Magic: The Gathering on your opponent's turn.
In Magic: The Gathering, you can block one creature with each of your creatures that are able to block.
No, you cannot block with a creature that has summoning sickness in Magic: The Gathering.
No, you cannot block with a planeswalker in Magic: The Gathering. They are not creatures and cannot be used to block attacking creatures.
Yes, you can tap or untap a target creature during your turn in Magic: The Gathering.
No, in Magic: The Gathering, you can only block one creature with one creature.
No, creatures with summoning sickness cannot be tapped in Magic: The Gathering.