I've completed the entire series in 5 parts, and I am fairly , certain that I've explored and found everything.
If you get stuck on getting out of the mansion check part 1.
If you get stuck on finding the location of the generators, check part 4.
If you get stuck on the music part of the Forgotten Mansion and just want to know how to get the medallion, watch part 5. More generally, part 5 has the wraps questline, and a walkthrough of the forgotten mansion.