I read this young adult novel in 2002, but I remember that the book from the library had some wear and tear, so it could have been published in the 1990s.
It's been some time, but I will try to give every detail I can. In the book, a group of children/teenagers/youths are transported to the future. They also somehow gain superpowers or strengths. I remember one male character's power was that he knew everything - even things that did not yet happen. Additionally, I distinctly recall one female character's power, that she could regenerate limbs. There may or may not also be a super fast character - I am shaky on whether this one actually exists.
In this future, there was some event, possibly a nuclear war, that severely depopulated the planet, and created large or fearsome rats or cockroaches. There was also a group of bad guys that this group of teenagers was in conflict with that might have had cybernetically enhanced limbs. I don't really know why they were fighting.
I do remember the ending fairly well. The female character who can regenerate limbs is trapped while swimming in a sewer, and is forced cut off her arm. Later in the battle with the villains, this same character is killed. At the end of the book, it turns out that the chopped-off arm in turn generates a whole second body of this recently deceased character.
I always had a problem with this ending - I remember thinking that a copy of me that grew off an arm is not me, and it drove me crazy even in grade school. All the other characters were fairly relaxed about the whole "body growing from an arm" situation too.
I thought the name was something like "The Omega Children." Think a common Greek letter like Alpha / Beta / Gamma and "children" or "kids" or something along those lines. Also, this whole name thing is rather unsearchable and quite possibly wrong.
I'm sorry if this one has already been asked and answered - I have forgotten so many details, all I really remember is this arm-regeneration thing.