If

The B sentences are grammatically correct, but they are old-fashioned, stylized or literary. Nowadays, we use 'if'.

Focusing on indirectness:

3a "He said that if he was not given access by noon, he would leave."
3b "He said that was he not given access by noon, he would leave."
3c "He said that were he not given access by noon, he would leave."

How are 3b and 3c different?

best regards

Let's try a different example. Let's say it is 10am in the morning and some guy named Michael wants access to a building. He says to me: "If I am not give access by noon, I will leave."

Then 11am comes and someone asks me about Micheal. I could say:

"He said that if he is not give access, he will leave." or
"He said that if he was not give access, he would

Hi! SheltieBites (I am a learner too) I think you can say these-
"He said that if he was not given access, he would leave."(if he is still out there waiting for the access to be given)
And you can say this-
"He said that if he had not been given access , he would have left"(If he has gone after waiting or it is 1:00 pm)
Thanks!

I think you are chasing your own tail by making up these nonsense. For a simple scenario as you described, I don't think anyone will go through the exercise to decide what time and which answer to use. You are making an indirect statement, you can keep it in present tense, So it is ok to say: he said that if he is not given access to the building, he will