Does it specifically mention anywhere in the rules about whether hindering terrain stops a figure during a knockback.
If there is a specific rule, can someone tell me where it says so. Thanks.

Knockback is not affected by hindering terrain.

what about other characters and the end of the board?

The edge of the map is like a wall. It'll do an extra click if it stops you.

Characetrs just stop you with no damage except when they stop you from falling off a roof (by occupying the non elevated square you'd fall into). Then they do 1 damage.