[MrPedantic]

Sorry, Hela, I had to give it an extra day! But I think I still agree with myself; except that I'm now not sure about this one:

e) I've been cheating on you since I KNEW you. (?)

Though if you insert "first" before "knew", it seems fine.

<...At some point I thought that the present tense could be used with the time expression "since" only with state verbs but "visits" above is a verb of process, so what is the correct answer?...>

For instance:

1. Since her mother died, she has visited the cemetery every day.
2. Since her mother died, she visits the cemetery every day.

Although #2 seems more comfortable, I'm not sure I would want to call #2 incorrect. It implies an expectation that she will continue to visit the cemetery every day; in #1, this sense of the future is much weaker, and the sense of the past much stronger.

Have a good Friday,

MrP