Rounders: rounders umpiring

a colleague says yes but I say no.

The batter steps out of the side of the batting square before the bowler releases the ball, the ball passes on the non hitting side of the batter! what does the umpire call?

When is a ball - a No Ball?

If a batter makes contact with a post and then 'swings' around moving past the 2m run off line whilst still holding the post should an umpire ask the batter to run on or due to the fact they made contact with the post before passing the 2m run off line are they 'safe'?

Is it okay as a batter, to sprint to first base and knock it over rather than slowing down to place your bat on the post gently? You would obviously pick it up and then remain in contact so long as you haven't turned the corner to make for second base. This would also help the umpire to see who got there first.

During a game one runner almost catches up with the one in front, they are both passed 3rd post when 4th post is stumped once! what decision does the umpire call?

I hit the ball and get to 2nd base when 4th base is stumped, I then run onto 4th post before the bowler receives the ball in the bowling square. What score do I receive?

the fielder successfully throws the ball against a base trying to get out a runner?

Is there a limit on the overrun rule? Obviously it is a 2m line. I tell my pupils they can continue in the same direction of the line until they manage to slow down. They then have to walk back and remain in contact with the post before stepping over the 2m line. Is there a limit on their over run?