I have Saharans and Kenyans. On Kenyans toward the tail the scales are raised, rough. The Saharans are smooth scaled all the way to a very fat tail.

The scar looks like a burn. I have a snake that was chewed on by a rat and it has random scales missing not the big area like yours. Shouldn't affect her in anyway. She definitely is eating by how big she is. She looks good!
Trey