I submitted a manuscript to a journal, and the status changed from Awaiting Reviewer Selection to Awaiting Reviewer Confirmation. It has been 1.5 months with no change in status. I'm curious if we are still waiting for reviewers to accept the review of the manuscript, like Awaiting Reviewer Invitation, or it's different, and the reviewing process is started already.

Another matter is the process of peer review from the aspect of a reviewer. Does a reviewer start the review just after they accept to review it, or they must wait until enough reviewers to accept the review and then the process begins?