The 4th Hokage Jiraiya learned rasengan and taught naruto who made an origanal rasengan
Im assuming you ment to ask who taught it to him. If so, then Jaraiya.
Naruto taught Konohamaru the Rasengan. Naruto said: "It's time i passed things down onto others." Maybe because the Sarutobi is Wind-Natured and because Konohamaru is like a brother to Naruto. Also remembering Naruto promised to fight Konohamaru for the title of Hokage, Naruto wanted him to get stronger.
naruto strongest rasengan is massive rasengan and nine tail fox rasen shuriken by:hao to
Nine tails [Kyuubi] Rasengan or the Vermillion Rasengan
When you have little healts and use normal rasengan red rasengan (nine tailed fox rasengan) must appears
seven-colored rasengan,kyubii rasengan,gelel rasengan, twin rasengan (kyubii and gelel rasengan), crescent moon rasengan,oodama rasengan (great ball rasengan), super great ball rasengan, naruto-shion chakra rasengan, and rasengan the spriral chakra sphere,Determination rasengan,tornado rasengan,dark rasengan
rasengan
Yes, he does
yes he does
No!!!!!!!........in naruto manga and episodes there are only rasengan,demon fox rasengan,odama rasengan,super great ball rasengan,raserengan,.ultimate rasengan, double odama rasengan, rasengan wind release, wind release rasenshuriken also rasengan riot, great ball rasengan barrage, mini-rasenshurilen, planetary rasengan, rasengan vaccum, and the Flash (Bijuu) Bomb to an extent Edit by Axel
a bigger stronger version naruto made himself to improve his rasengan