I wanted to change the engine mounts and some gaskets of the 240.

for the mounts on skandix for both there is the "heavy duty" version: does it change anything in terms of duration or is it for specific types of engines?

both give them for every engine except B20

left
https://www.skandix.de/en/spare-parts/engine/engine-mountings/engine-mounting-left/1000048/

left heavy duty
https://www.skandix.de/en/spare-parts/engine/engine-mountings/engine-mounting-left-heavy-duty/1028677/

right
https://www.skandix.de/en/spare-parts/engine/engine-mountings/engine-mounting-right/1000049/

right heavy duty
https://www.skandix.de/en/spare-parts/engine/engine-mountings/engine-mounting-right-heavy-duty/1028678/

for the differential from what I've read around there is more than one model, mine has the drain plug. is the gasket correct?
https://www.skandix.de/en/spare-parts/drive-train/wheel-drive/differential/gasket-differential/1000205/

for the valve seal
https://www.skandix.de/en/spare-parts/engine/gaskets/rocker-covers/gasket-valve-cover/1000176/

I read that it should be paired with a new "half moon". Bullshit or does it make sense?
https://www.skandix.de/en/spare-parts/engine/gaskets/rocker-covers/halfmoon-valve-cover/1000178/