Not really
but Sasuke's getting darker day by day...
i would have to say "Suigetsu" According to sasukes flashbacks in recent shippuden episodes Sasuke thinks that Naruto Uzumaki And Suigetsu are the same personality wise. :D
yes u can change your personality
No
Really good!
Sharingan
He doesn't have one.
Suaskes (?) If you're talking about Naruto, Sasukes parents actually get killed by Itachi (Sasukes older brother)
Yes, it is alaways possible to change your personality. You just have to figure out, what you want to change about your current personality, and figure out how you are going to do it.
July 23
Fugaku and Mikoto Uchiha
July 23rd - Pisces
If you mean the time when he fought Naruto in 1 tail form at the Vally of the End, it's because of the cursed seal.