hi @Jason thank you for your answer!
I had not idea MoveNet was out, I will check it out by sure.
About the question 2, if I understood well, probably my problem is most on the side of “regular computing vision” rather than machine learning itself:

I can control the printed forms: I can add QRCodes or AR markers if needed…
I know in advance the layout of the form to process.
I guess the main challenge is that the capture should be done with a phone or in front of a webcam rather than using a flat scanner. that’s why I imagined that AR markers may be of help: to determine the axis of rotation of the sheet, apply some kind of “inverse transformation” to “flat” the captured picture and then compare the circles with the answers.