Manage my posts is in the left column of your feed and of your profile. It opens on Published, with a search box for your own writing and Sort by: Newest.
After you submit a post to a community, the tab to check is not Published. It is Rejected — that is the only place a declined submission appears.

Every post carries a small header of its own, and it is the most useful thing on the page.

A post is not fixed to the destinations you chose when you wrote it. Publish elsewhere submits the same piece to another community whenever you like — a month later, a year later, when you join a network where it belongs.
A piece that landed well in one network is usually worth offering to the others you belong to. Nothing is lost if a second network declines — the first publication stands.

Check Rejected first, then See details on the post under Published — a post can be live in one network and still under review in another.
Yes — Publish elsewhere on the post’s strip. It goes to that network’s review like any other submission.
Yes. Edit it in the Rejected tab and offer it again, here or to a different network. Posting to a community covers what reviewers look for — and what will never pass, such as anything commercial.
Manage my posts, in the left column of your feed and of your profile.
The same four as everywhere else — see Your feed for the key.