On a Non OA you will stamped in for 365 days on each entry or up until your insurance is valid until. If you enter just before the visa expires and have the relevant insurance you’ll still get the full year. This “second” year is not multiple entry. If you want to keep the stamp “alive” you’d need to get a re-entry permit (single or multiple).
No one knows how many exempt entries you’ll get away with as it’s up to the individual immigration officer you hand your passport to. Perhaps two maybe eight who knows.
Only going by current posts on FB and YouTube. If on an ED visa you can forget about trying for an account. Even the agents can’t do it. Changed a few weeks ago. I have no direct experience so perhaps it may work for you.