Update
I was finally able to recover my email. They gave me an option after I reported to Google Support. They wanted to know about the exact month and year. in which I opened this email. They allowed me to enter new password. because I able to entered the correct information there.
One more good news is that. The hacker did not change the original mail from my account. He set a strict security on my email and he probably sold the account with either the original email. To get a higher price. I don't know exactly if something like this happened. I was able to recover my Bitcointalk account with email. But my account is now in a lot of danger where two red Trust and one red flags have been given by DT. I am requesting to remove the red trust & flag from my account.
Note- Thanks to everyone here who showed me different ways to help. Although I got my Bitcointalk account back with my email. I don't know if the red trust in my account will be lifted now. However, it does not motivate me. But it's too big for me to get back my personal documents, including my email.