Approvals or Selects?
Approvals: the client judges every photo — for sign-offs, e.g. photos for publication. Selects: the client picks up to N favourites — for choosing what you will edit.
I re-edited the photos. How do I ask again?
On the gallery's Approvals tab press “Reset all answers” (or “Reset” on one person's answer), tick that you understand and confirm. The answers and their history are deleted — this cannot be undone — and the client can answer anew. If the answers are locked, turn off “Lock answers” too. It does not count as a new question in your plan, and verdicts already pulled into Lightroom stay in your catalogue.