I am at mastery for F1 in RC and HBP but not the rest

Should I purchase the next foundation in order to still progress on those two? 

You can always buy f2-f4 when ever you want to.

Did you test yourself for mastery of each element or did you just look at the video and think to yourself I can do that?

Pseudo planche push ups, Bulgarian ring rows, bent arm chin hangs,  are all harder than you may think.

Don't let your elbows flare out to the side with the push ups. For the Bulgarian ring rows, pull your hands further apart before pulling your body up and hold the top position for a second or two.

The dips in the course are the ones that target the tricep more than the chest.

Jake Oster said:

Should I purchase the next foundation in order to still progress on those two? 

Yes, if you have mastery on both this elements in F1, then continue then in F2.

Welcome aboard,

To my mind is difficult to achieve HBP/PE3 mastery (PPP's) without a strong sPL/PE5 (planche leans). 

I mean, maybe you've doing the rep scheme, but the form is important and the form is just exactly as a planche lean is.

The advice would be: go to check your form and post form check to get another POV.

About your question, of course you can (and should) advance.

^^^What Adriano and GoldenEagle said. Make sure that you can perform mastery (this means form matching the demo video throughout all of your sets with only the paired Integrated Mobility exercise as rest between your sets) of each progression starting with the first, and can perform mastery of the integrated mobility exercise as well. If successful, then try to do the same with the second, and then the third, and so on. If you cannot perform mastery of the reps/sets, and form, and integrated mobility you cannot move on to the next progression.

Also, don't assume that just because you can perform mastery of PE6 that it means you can do so for PE1-5. You need to work through/demonstrate mastery in them in order.