Optimal Position Rotating system?

Somewhat related to a topic yesterday. What do you think is the optimal system for getting players experience in different positions (or not)? We are talking for u9 boys 7v7 age group in our situation.

1. Have each player play multiple positions, say 2 positions per game. They play these same 2 positions all season.

2. same as 1, but every month or so they switch up the 2 positions.

3. Each player mostly just plays a single position per game with a few players playing multiple positions to balance playtime. The players rotate to different positions every month or so.

4. Same as 3, but no rotating positions. They play the same position all year.

5. Other. What's your vote for optimal position rotations?

Our coach hasn't been rotating much so far this season particularly for the defenders.

Our team is not very high level so I am hoping he's letting everyone get situated a bit before rotating them more as the team gets up to speed.

Seems you could make an argument for 1, 2 or 3 being optimal but our player has fallen more into scenario 4 last couple seasons. CMF last year and CB so far this year.