This is a FAQ but is there a summary like this:
- To upvote a Lemmy post from Mastodon, add to favorite(?)
- To see a Mastodon post from Lemmy: not possible(?)
- To post from Mastodon to Lemmy
- To post from Lemmy to Mastodon: the sublemmy has a Mastodon account just follow it.
- To post from PixelFed to Lemmy?
- To post from Lemmy to PixelFed: not possible (?)
- …
I’m not sure if all of your points are covered, but this page has fediverse tips and an active mastodon account where you might be able to ask for the remaining scenarios to be covered
https://fedi.tips/
https://mstdn.social/@feditips