I am submitting evisa application.
I have purchased one way ticket to Ahmedabad India.
So port of entry will be Ahmedabad airport and I have mentioned two places to visit.
Ahmedabad and Mumbai.

But not sure what should be exit port because I am not sure myself from where and when I will fly back from India..i.e. not sure between Mumbai airport vs Ahmedabad airport

So please advise what should I put ..and if I put mumbai for example..and I want to exit from Ahmedabad airport ..will that be a problem or vice versa?

On the e-visa site there is an 800 number you can call and maybe ask them all the questions you have been asking here.

Make a list of questions, sit with a paper and pencil, ask questions and write whatever they tell you. Maybe it will help you fill the form.

I realize the e-visa application is not easy, but take one step at a time. I hope your questions will be answered by the visa office workers and your problems will be solved.

So, Monday morning, do this task and do not wait longer asking questions here as we are not experts, but are just experienced travelers, who may not have faced the same questions you are concerned about.
Good luck.