Grimrock

The bag turned out to be simple, although I initially assumed (wrongly) that it only moved from locked cell to locked cell. I got into the blue crystal room and wiped out all the monsters and found the secret door that revealed a another key. However, there are two keyholes in the blue crystal room ...

I see the bag which goes from cell to cell depending on how many times you push the buttons. I have not been able to get to the bag as yet.

Is it possible to lose a key? What if you accidently give an item to a player who has no slots available? Does the item stay around? The only solution I can think is to go back to my last 1st level save.

Yes I did find a key for the first door in the first corridor to the right after I killed the snails and I did find the secret door in that room. However I did not find a key in either the transporter room or the skeleton trap at the end of corridor of the second corridor going right.

I found 3 keys on level 2 so far, but there are four locked doors. I am stuck at the second iron door into the blue crystal room. I have fround all the secrets up to this point on level 2, but I cannot find the 4th key to open the iron gate into the blue cystal room. Any help?

I guess I am not finding weapons before meeting monsters. I need to keep my eyes open

This seems like a dumb question but I have read the manual and gone thru the tutorial. How do you attack a Monster? How do cast spells? How do fire a bow?