You don't. You can't get back into the dungeon through the library (once you have gotten the cheese and thrown the switch). You have to enter through the "back way".
(see related question)
no
You dodge the ball.
Walk to the right.
keep pushing it
no there is not a cheat to get past the dragon on astro knights
just wait for the fist to come and then duck down when it jumps up.
You have to find and repair the saucer that crashed past the mill. (see related questions)
It isn't rock, it's dirt. (Surprise) You can push hard and it will collapse. == ==
Reach and repair the saucer Excalibur in the mud swamp past the mill. (see related questions)
You have to hold down the mouse and when the mouth opens you shoot. You need to do it three times.
the swamp is past the wind mill in the mud
you need to defeat the dragon