In older version of PS was config setting cleanup: player-inactivity-purge-days. I tryed to add this in 9.8.3 but it dosn't work. Same with /ps admin cleanup remove [days]

How can I remove old plots ? Example older than 45 days.

This was added to the dev versions. Download the latest one from my Jenkins.

You can.

Nothing should need to be changed when updating to 10. Maybe the note block got erased cause the world data didn't get saved? Test again with /save-all. PS doesn't erase world blocks for no reason.