If the mailman cannot gain access into my condo for any reason does he save the mail & put it into my mailbox the next day?

No, they do not hang onto the mail. They will return it to the post office. If you dont want mail coming to where you live, get a post office box or private mail drop.

No, he gets to sell it all on ebay.

yes

unless the mailman REQUIRES signature for a package or registered or certified mail, or a package is oversized, he can leave items in your box TODAY.

Anytime delivery can't be made, for all sorts of reasons, mail is returned to the office. An attempt will be made the next day there is mail delivery. If the cause of non-delivery lasts more than three days, the carrier will place the mail for affected addresses on hold. Delivery will resume once the carrier sees that the cause has been resolved, or the customer comes in to get their mail and tells us that the problem is resolved.

Because he emails it to you durr

probably, but it's best if you contact the postal station that serves your area