I really like the concept of how changing the present doesn't affect the past, but it does vice versa. That's clever and can make for great puzzle design. I will say that it's important to remember the enjoyment should lie in figuring out the puzzle more than merely executing it, because figuring out I had to move the three boxes in a certain order to platform-jump over the gaps was fun, but because of the amount of boxes the execution became just a bit tedious. I also like how you can in fact off yourself by moving into walls, adds another thing to consider.
If you should consider working on this more, it might be fun to integrate more environmental design that explains and hints at what would decay or otherwise disappear over time, like, idk, a hot environment where a river runs dry, plants decay, etc. Right now, because nothing about the environment tells me what will be different in the other timeframes, it's more trial & error. There's lots more puzzle potential here!
Another thing, this one may be purely me, but the constant zooming in and out did start to give me a little bit of nausea. Just putting that out there.
Anyway, fun concept. Clean art and good audio. I also like the animations on the character, the jump looks a little 'stretchy' which I thought was fun.