If a creature the defending player controls can't block the target creature for any reason (such as being tapped), then it doesn't block that creature. If there's a cost associated with having a creature block the attacking creature, the defending player isn't forced to pay that cost, so it doesn't have to block in that case either.

If a spell's kicker cost was paid, the spell is "kicked."

If a card or token enters as a copy of a permanent, the new permanent isn't kicked, even if the original was.

If you put a permanent with a kicker ability onto the battlefield without casting it, you can't kick it.

To determine a spell's total cost, start with the mana cost (or an alternative cost if another card's effect allows you to pay one instead), add any cost increases (such as kicker), then apply any cost reductions. The spell's mana value remains unchanged, no matter what the total cost to cast it was.

If you copy a kicked spell on the stack, the copy is also kicked. If the copied spell is a permanent spell, the token the copy of that spell becomes when it enters is also kicked.

The kicker ability doesn't let you pay a kicker cost more than once.