About The Monkey Island 2 puzzle...
If you are mentioning the big door in the LeChuck's dungeon... it is a big door with dozens of padlocks, but there's a small door in the big door (Like a "dog's door"). You just have to open that one and ignore all the other doors. Now I remember you had to get a key somewhere in this part of the game, but I don't remember if it was for this door. Anyway, I got past this part the 1st time I played it. What really got me stuck was that you had to "hipnotize" the monkey playing the piano and how to do it (I won't spoil for those who maybe haven't played the game).
Dreamweb - In the church, very close to the end, the way you find the secret door. That was SILLY (If anyone ever played the game), at that point I was just trying random stuff. This game is SO full of red herrings, it's just not funny. And the ending was pathetic. This game was good only in the beggining, then the plot gets destroyed and the puzzles get alls stupid. For me it always felt like the developes rushed out the game, because that's how the last 2/3 of the game feels.