Any can be written about! A fill must be 1 fandom. 1 relationship under that. 1 freeform tag under that.

This applies to the same characters plus the hurt part too. If you request A/B (hurt A), A/B (hurt B), A/B (both hurt) then someone only has to pick one of those, they can write, or draw if you requested art, A/B (hurt B) and they don't need to create a work where first just A is hurt, then just B is hurt, then both are hurt.