Add old particle physics from 1.12 to newer versions of the game
also is 1.16.5 still going to be supported / get new features?

I'll look into the particle physics and see what I can do.

In regards to backporting features, yes, 1.16.5 is still supported and will get the 3.1 eye candy update when I have the time. I try to support the most recent two versions of the game. Right now that is 1.17 and 1.16.5. It takes longer to get the 1.16.5 version of the mod up to date because the mappings are different and 1.16.5 uses a different project structure than 1.17.