I'm currently running Mac OS Mojave 10.14.6 in a 2017 MacBook Air with an i5 and integrated graphics.
About the wooden plank passage, I think I have trapped myself somehow while playing. Don't know really how to explain, but the scenario was the following:
I needed to open the electric locked chest at the attic in order to get the last photo. The attic gate was locked because the statue was over the plate that releases the chest lock. I went through the plank many times and it fell so I couldn't reach the attic from the other side. So, if I moved the statue to get to the other side, the chest got locked again. Was I missing a way to keep the gate open and the chest unlocked? Sorry if my description isn't very clear, English is not my native language.
When I got some more time I'll try the alternative endings too, for sure!