No, Most lease contracts have extenders in them in some form. Also if they still occupy the space you can not lock them out. You will have to apply due process to get them out.

Not unless you want to be sued. Changing the locks constitutes an illegal eviction.

Did either of you notify the other that the lease will not be renewed. If not, most states accept that the lease has been renewed , at least on a month to month staus. Did you lease addess renewal and notice?

You can not lock them out, that is an illegal eviction and you could be sued for damages.

One of two things has happened, ( depending on the terms of the lease) 1. the lease renewed 2. they went to a month to month rental.