Spoiler : :
1. Vincent Eisenhower was possesed by the spirit of his late wife, who proceeded to stab "herself" and thus renders this whole situation as a suicide-murder. Though there are two ways how this could've happened.
a) He summoned his late wife's spirit in his room and was possesed by her, resulting that she has gone to the safe room and killed there Vincent. As to why the body didn't fall to the front - maybe she just wanted to amuse herself and leaned back, so that the body would fall backwards? I mean, we don't know her personality... or we do, when those green texts in the beginnings and endings of each parts were her. So yeah, she could just enjoy the show when Phoenix and co. would investigate the case, never hoping to find the real murderer. Oh and about the missing room key... maybe she just throwed it somewhere or rather decided to frame an innocent? Then whoever it would be, would be the "victim" of this.
b) Concluding that it would be far too risky to summon his wife in his own room, Vincent decides to do this in the safe room. There he proceeds to lock the doors and then summon her, getting himself killed in the act when he's possesed by her. You may wonder what's so different about this option besides that he's going to do the "spirit channeling" in the safe room... well, we all know that in this scenario, the room key should have been on his body, but this is were Sunny comes into action. That little girl has already stolen something, so it could be possible that he bumped into her on his way to the safe room. He either lost his keys in this accident or Sunny stole it.
2. I don't think that this is true, because it's totally ridiculous, but I can give it a try nontheless; Vincent Eisenhower wasn't dead when Frost opened the door. That's because she's the one who murdered him right after she discovered him unconsiousness on the ground. She stabbed him and because she had gloves on, there wouldn't have been fingerprints (not that it matters, because they can't find it out without proper equipment) and if she would've gotten blood in them, she could've just wear them on the wrong side. Who knows, maybe it looks exactly like the other side, so no one noticed it.
a) He summoned his late wife's spirit in his room and was possesed by her, resulting that she has gone to the safe room and killed there Vincent. As to why the body didn't fall to the front - maybe she just wanted to amuse herself and leaned back, so that the body would fall backwards? I mean, we don't know her personality... or we do, when those green texts in the beginnings and endings of each parts were her. So yeah, she could just enjoy the show when Phoenix and co. would investigate the case, never hoping to find the real murderer. Oh and about the missing room key... maybe she just throwed it somewhere or rather decided to frame an innocent? Then whoever it would be, would be the "victim" of this.
b) Concluding that it would be far too risky to summon his wife in his own room, Vincent decides to do this in the safe room. There he proceeds to lock the doors and then summon her, getting himself killed in the act when he's possesed by her. You may wonder what's so different about this option besides that he's going to do the "spirit channeling" in the safe room... well, we all know that in this scenario, the room key should have been on his body, but this is were Sunny comes into action. That little girl has already stolen something, so it could be possible that he bumped into her on his way to the safe room. He either lost his keys in this accident or Sunny stole it.
2. I don't think that this is true, because it's totally ridiculous, but I can give it a try nontheless; Vincent Eisenhower wasn't dead when Frost opened the door. That's because she's the one who murdered him right after she discovered him unconsiousness on the ground. She stabbed him and because she had gloves on, there wouldn't have been fingerprints (not that it matters, because they can't find it out without proper equipment) and if she would've gotten blood in them, she could've just wear them on the wrong side. Who knows, maybe it looks exactly like the other side, so no one noticed it.