Re: itachi's gift
Kekke genki could be any trait specific to a clan.
Monstrous healing ability might be a precursor to being a vessel for all bijuus.
Naruto is most likely a senju descendant through one of his parents kushina or minato could have been of senju decent, we don't know.
so his kekkei genkai is something to do with his healing ability.
Multiple kekkei genkais are a possibility also, but with the foxes chakra mixed with narutos its hard for them to be distinguished.
itachis gift to naruto was prob a weapon rather than a jutsu or special chakra boost. Naruto only misses a good weapon, he can learn difficult jutsus, and he already has chakra to kill.