InterWorld (2007) by Neil Gaiman and Michael Reaves?
InterWorld tells the story of Joey Harker, a very average kid who discovers that his world is only one of a trillion alternate earths. Some of these earths are ruled by magic. Some are ruled by science. All are at war.
Joey teams up with alternate versions of himself from an array of these worlds. Together, the army of Joeys must battle evil magicians Lord Dogknife and Lady Indigo to keep the balance of power between all the earths stable.
The Wikipedia summary has Joey meeting a guy called Jay, Jay dying and the other Joeys resenting the first Joey:
Joey approaches it and as Joey tries to free the mudluff, a giant serpent (Revealed in the second book to be called a Gyradon) appears, biting Jay. The mudluff kills the serpent but Jay was already dying. Before he dies he gave Joey the direction to Base Town, where InterWorld HQ is. [...]
Many of the other Joeys initially resented Joey for causing Jay's death, but soon come around about him as his skills improve.
And the cover has a red-haired kid and some flight-looking traits:
Found with the Google query
book "* dimension" "versions * himself" site:goodreads.com.