Future Perfect Continuous (Future Perfect Progressive)

I have been an entrepreneur for the past 20 years. Generating my own income in various ways. I'm about to embark on a new venture and it's scary. What do you think about being an entrepreneur? Do you think it's a viable option in the current economic climate? Does entrepreneurship come naturally or is it born out of necessity? I would love to hear your thoughts.

Spring is a time for fresh starts.

Sorry to disturb great native English speakers. Queries about eight real sentences with modal verbs. 1a. You can take the car if you want. 1b. You may take the car if you want. 2a. Can I borrow your pen for a moment? Yes you can. No you can't. 2b. May I borrow your pen for a moment? Yes, you may. No, you may not. 3. May I play ball this morning? No, you cannot, but you may play this afternoon. 4a. Could I use your phone? Yes, of course you can. (Not: Of course you could.) 4b. Might I use your phone? Yes, of course you may. (Not: Of course you might) 5a. Can you open the door? Yes, certainly. or I'm sorry I can't. 5b. May you open the door? Yes, certainly. or I'm sorry I can't. 6a Can I ask a question? 6b. May I ask a question? 6c. Could I ask a question? 6d. Might I ask a question? 7a. He must be tired now. 7b. He may be be tired now. 7c. He might be tired now. 7d. He could be tired now. 7e. He should be tired now. 8a. She must have missed the train. 8b. She may have missed the train. 8c. She might have missed the train. 8d. She could have missed the train. 8e. She should have missed the train. Question: ① I guess that the meanings of each group are almost the same, but their (the group) tones are different, Is my guess correct? ② Does every group have the same meaning? ③ Is each group grammatically correct? or, Which is/are grammatical correct?