Without socks, the players would get blisters
The NBA players wear Beats by Dr.Dre
No current NBA players wear number 28.
Those are actually called "shooting sleeves" and basketball players wear them to help maintain their shooting form.
It depends on the player and their sponsors, the most common are Nike and Under Armour
NBA is sponsored by Adidas so he can not wear them in games but Kevin Durant is sponsored by Nike so he does have his own elite socks. NBA game socks are made by Bare Feet not adidas.