The director of Pretty Rhythm confirmed on twitter that Pretty Rhythm Rainbow Live will not feature characters from the two previous seasons: Pretty Rhythm Aurora Dream and Pretty Rhythm Dear My Future. He also said that you don’t need to watch them to watch Rainbow Live.
There goes my hopes of a final arc with Naru, Bell and co accompanying Rinne in her dimension travels and meeting the past characters… I guess there’s still
Yamada Tanaka’s and Penguin Sensei cameos to look forward to.
Now that we’re 100% sure about this, I can without worries write a “how to get intro pretty rhythm” post and say that you can either start with s1+s2 or watch s3 from the start.