I am currently playing Dungeon Master (original version) for the first time and thought that I would create a new topic for me to solicit help

I am really enjoying the game and have been doing pretty good so far...have been startled several times when creatures surprise me - especially when my volume is a little too loud.

I am currently on level 5 and there is 4 rooms. In one of the rooms there is a button and when I press it a wall opened up and I find more buttons. I believe I have pressed them all and it seems like nothing is happening although I just got surprised by a green creature that shoots poison at me (so far this is the creature that has killed me most). He must have come from somewhere but I don't see another hallway or room or anything. I am assuming that pressing the buttons must have opened and closed something again. First question - is there a spell to protect from getting poisoned? And second question, is there a proper sequence to follow for pressing the buttons? If I have already pressed them all in the wrong order, please tell me there is a way to "reset" so I can start again - I failed to save my game before I started in this room
