Answer 1

Ill run you through some basics:
The reason for the "night" has to do with the fog trigger. It decides which colors everything is. The default is a foresty daytime one, but you mightve accidentally placed another one and then deleted it?
A red end trigger (red flag) needs to be tied to enemies to function "properly", right now the level will seemingly "randomly" end when you start climbing towards the house, since the game loads the trigger with no enemies tied to it. If you want the level to end when you get to the house, use a purple flag instead and hold shift and click while its selected to place the area which will end the level when the player enters it.

As a non-basic sidenote: an alternative could have been to use dustblocks for the diamonds, and then you can attack to "mine" them