I’m having trouble with the upper cut into the spin at the beginning are there any tutorials anywhere for an in depth look at it?

Where exactly is this? I assume you're talking about a boosted uppercut, but I can't think of any that are at the beginning of the run. Here's a few videos that might help you on that tho:

There’s this 20 min speed run on YouTube where a guy does it. I got it once but I’m having trouble doing it again

I’m thinking about this run

I still don't understand which uppercut you're talking about. Could you provide a timestamp?

The one right at the beginning

Well, doing the flag proxy isn't recommended until you're at a very high level. But in general for boosteds, did you watch the videos I linked?