Yes you may renew it after the expiration date.

Yes this isn’t an issue at all for purposes of submission.

No not if the entry is legal and within the validity of the visa.

You may amend the record at time of interview.

This may be done at the time of interview.

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No not through H4 but visitor visa may be possible.

Worst case, USCIS will reject and you can refile.

A departure while the case is pending deems the case abandoned.

The updated form alone should suffice.