Can the Byakugan evolve?
Hear this out loudPauseA Byakugan can
evolve into a Tenseigan under unique circumstances; this was first showcased through Hinome Hyūga, the transmigrant of Hamura Ōtsutsuki.
What is the golden Byakugan?
Hear this out loudPause"golden byakugan", is
just the fan fic alias for an upgraded byakugan. It came from zetsu's yellow eyes and byakugan like eye sight. Imo it is very probably that there is a higher level of the byakugan but it is very improbable it will be called the, "golden byakugan".
What is the strongest Byakugan?
Hear this out loudPause1
Kaguya Otsutsuki Undoubtedly, the strongest Byakugan user in the story was Kaguya Otsutsuki, the mother of the Sage of Six Paths.
What happens if someone has both Sharingan and byakugan?
Hear this out loudPauseThe Sharingan and Byakugan are one of the three great in Narutoverse. While the Sharingan lets the wielder traumatize the opponent, the Byakugan is more physical, in the sense that you have the ability to distort the flow of chakra.
A combination of the two would be lethal.