(SOLVED) How to I rotate a pasted image to a background?

[Ofnuts]

2.10 works exactly like 2.8. I cannot tell what your problem is because your screenshot is too small (please add a full-scale JPEG). Where is the cat pasted from?

The operation order is:

1. paste the cat (this creates a "floating selection")
   
2. rotate/move/scale the cat using the Rotate/Move/Scale tools
   
3. Anchor to target layer (although usually it is best transformed into a layer of its own: Layer>To new layer).
   

(I removed the script because it is unrelated to your problem and this could becomes an obsolete version)