Saller_ar "most don't", can you give more examples?
player_sustainAmmo doesn't work on T6 yes.
Either write a gsc script that does the same or easier use a mod menu https://forum.plutonium.pw/search?term=mod menu&in=titles&matchWords=all&categories[]=23&sortBy=relevance&sortDirection=desc&showAs=posts
As for other commands I could answer if you give examples. Some commands aren't meant to be used and some others are bugged yes but I doubt that most commands don't work