Although its mentioned in the instructions that you must create a public repo on Github, its not perfectly clear to me if this is compulsory. If so, how much of the source code/files must be included in the repo to be eligible to participate?

Any answers would be great.

Yeah, I have the same questions.
I get that GitHub is supporting this jam, but the actual submission process appears to be via itch.io.
So...why would a solo dev need a GitHub page? Are they disqualifying people without one? Are we expected to submit in two places at once?