Thanks for all your patience; this forum is really clarifying a lot of things to me, hope it works the same for you.
I cannot match the sense of this sentence in the Q&A, to justify taking an OCS boat arrival time as good for the time limit:https://www.racingrulesofsailing.org/cases/1109?page=20
Would the answers for Questions 1 and 2 be different if boat A had not returned to pre-start side of the starting line before starting?
No. The answers to both questions would be the same.
requires the boat to sail the course, and it does not mention starting....(omissis) ... it makes no difference for the purpose of rule 35 whether the boat returned and started.
My conflict: true that rule 35 does not directly mention "start", but it does mention "sail the course as required by rule 28", and rule 28 states "a boat shall "start", sail the course etc.."
So a boat not complying with the definition of "start" is not sailing the course as required by rule 28, and so she do not (should not) meet the condition asked by rule 35.