Can Goku use Super Saiyan Rose?
Super Saiyan Rose is Goku Black's version of the regular Super Saiyan that surpassed the power of Super Saiyan God and evolved naturally into SSGSS/A differently colored Super Saiyan Blue due to his status as an actual god with natural god ki.
Is Super Saiyan rose stronger than Kaioken?
SSBlue Goku lost to rose, so you can say
rose is stronger than blue, but past that point Goku did not really have any measurable competition unless you want to count Hit, but he's hard to compare to rose, and UI Goku could probably handle any level of SSRose, so SSRose with kaio-ken is just somewhere in between >SSB < ...
Why is King Kai dead?
Despite numerous chances to bring him back to life, King Kai has remained dead in the Dragon Ball universe. ... When Cell threatened to destroy the Earth by self-destructing,
Goku used Instant Transmission to bring him to King Kai's planet, thus sacrificing himself, King Kai, Bubbles, and Gregory to save Earth.