None of the major characters die, contrary to what some alleged leaks might have claimed.

Rocket is indeed confirmed to be a mutated earth raccoon. By the end he embraces his... Raccoon heritage? I guess?

The High Evolutionary's interest in Rocket is that while he is an otherwise crude prototype he didn't intend to be special, he is literally the only one of his creations that was able to innovate rather than just memorise formulas, so he needs to study Rocket's brain in order to learn how this came to be and how to implement it in future creations.

Despite the High Evolutionary explicitly using earth as a basis for his counter-earth, down to mutating its creatures and copying human technology for them to use, he is not from earth himself. He just kind of picked earth because he thought it was a suitable template.

Phyla-Vell is in this movie. In case you were wondering about her origin since she can't both be half-Eternal or Mar-Vell's daughter because the MCU had changed so much about them, she is a creation of the High Evolutionary. It is possible that he might have uncovered the Celestials' formula for the Eternals or maybe he used Kree as a basis but that is not stated.

Rocket has died

I remember the "leaks" earlier that Raccoon dying was a fake-out, that actually Drax would die. Nobody dies? Meh. Does Gamora get her other self's memories, at least?

No, she does start to kind of get why her alternate counter-part might have gotten along with the others but she does not gain any of those memories.

They made Rocket and Phyla-Vell both creations of the High Evolutionary. I get why in both cases but I'm not sure it had to be that way in either. Like sure, what Rocket is can be considered so similar to the New Men that he might as well be one of them, I just don't know if it was necessary because Half-World might be fine as is, it doesn't actually conflict with anything the High Evolutionary does. As for Phyla-Vell, yes she was going to be something else because her original origin would make no sense in the MCU, but they didn't need to make those previous changes, the Eternals did not have to be robots, Titan did not have to be a dead planet and Mar-Vell did not have to be a woman who dies before really doing anything.

Then there is the High Evolutionary who is made out to be an alien here because... He couldn't get onto a spaceship? The problem by having him be an alien here is that his decision to use human culture and other earth animals as the basis for his experiments seem somewhat random when he's not human himself. I understood why Drax and Mantis were made into aliens, it arguably wasn't that important for them to be human but the High Evolutionary not being human just seems... Off.

And finally, Peter's grandfather is named Jason... Not sure if that's just a reference or if they literally split J'Son into two characters. If it's the latter, are they seriously going to go as far as to say Peter is a Spartaxian after all?