1st) How can I pause the game (meaning, not allow any other programs to run) while I display a menu and some text on a panel?

2nd) Can I show a block at the top of my screen to display different stats and such (maybe a health bar), but not have any level underneath the block?

3rd) How could I stop an entity from leaving a 800x600 region/ or detect if an entity ran into a door or something?

Sorry for the long list everyone, but I could use some help. THANKS FOR EVERYONE WHO HELPS ME!