There are a few times, when he did it. One can probably say that he learned it, but he also seems to keep forgetting it, since he keeps going back to the clone method. He should have put hundreds of clones into learning the one handed rassengan. It would have been a lot easier to learn the Rassen-shuriken, then. It could have saved him some time, overall.

*Episode 86-94 Naruto OG* Naruto first learns the Rasengan. Mastering the technique 4-5 years later in the coldest way possible.. 🥶💯 *Episode 379 Naruto Shippuden* After Obito talks trash about Minato, Naruto says what needs to be said then proceeds to slam a fully perfected, single hand, sage mode, Rasengan into Obito’s back just like his father did on the night he and Kushina died to the 9 tails. 🐐💯 (With a little help from Tobirama who let’s him finish speaking before delivering Naruto to Obito)

Yes he learned how to use it by himself

THE ANSWER IS ITS ONLY WHEN HE FORCE TO FUSE ONLY WITH KURAMA! LIKE KILLER BE ON HIS PARTNER USE KYUBI CHAKRA THATS ALL