Originally Posted by edy4eva

1. Yes.
2. Yes.
3. No, you will have to disembark and board again because technically you're on two separate tickets/boarding passes. Someone did it with 2 passes and caused a stir for moving up front to his assigned seat while on the ground, from memory he did a trip report either here or on Airliners.net.
4. No requirement to stay onboard, but one reason they might not let continuing passengers out is to save time/minimise the delay if the flight is behind schedule. Your case is different though.