Cut off one head, two more shall take its place

There is a creature with many heads, one knight wants to kill it. He can cut 1, 7 or 11 heads off.

If there is any head left:
I) After cutting 1 head off, 4 heads will grow.
II) After cutting 7 heads off, 1 head will grow.
III) After cutting 11 heads off, 5 heads will grow.

Creature dies when there isn't any head left.

Can knight kill it
1. If it has got 100 heads?
2. If it has got 99 heads?

Image Credit: Flickr Leo Saldaña.