Hi! If we talk about the first game there is a switch you need to press in order to deactivate the spikes. For the second game you got a pair or keys so you still have one key left to use when backtracking at the beginning of the dungeon. If you ever get stuck i made a letsplay of the 2 games on my second youtube channel.
Af : https://youtu.be/ug8xIqYDqic
Af2 : https://youtu.be/rxNmCXt7Fy0
Hope it help! :D