Re: Itachi And Sasuke Element
Sharingan cannot copy all non-kekkei genkei jutsu. For example, the Minato's flicker jutsu can not be copied. I'm not sure if Kakashi copied the Rasengan or simply learned it, or some combination since there are no hand signs involved.
People can hold up to four elements unless they have the Rinnegan. They only have an affinity to one (Uchiha may be different because they all have fire, and Sasuke seems to have lightning too), the rest, up to 4, can be learned. However, Kakashi's water jutsu are weaker than someone who's base affinity is water I think I heard that. However, he matched Kisame and Zabuza, so I don't know about this. I thought it was mentioned during the Kakuzu vs. Kakashi fight.
I don't think they can execute jutsu they don't have some affinity for. I'm sure Kakashi has copied fire jutsu, but he only uses fire in the anime, correct? He might be able to make the hand signs but not exhale anything but basic chakra or nothing. I can't say.
I think that the above is correct. If I'm mistaken, I'm certainly open to correction.