Hacker managed to change my account's e-mail id & then the password.
I noticed it at 3:45 PM GMT & got my account locked using the link the forum sent me on my e-mail id along with e-mail change notification.
That's the address which I had staked last time: https://bitcointalksearch.org/topic/m.19862993
It belongs to my Lykke Exchange account. I have access to it. Can send screenshots and other proofs but won't be able to sign a message from it as it's exchange address.
How shall we go ahead now?
Sorry to see that your account got hacked. As per Theymos's instructions, you can use any address (even which is not staked) whose private key you own:
Often, you need to prove ownership of the account with a PGP or Bitcoin signature. This has two steps:
1. You need to show that the PGP key or Bitcoin address is associated with the account, for example by referencing an unedited post in which you posted the address.
2. You need to sign an appropriate message with that key/address.
You have so many addresses mentioned in your earlier posts that are unedited like
https://bitcointalksearch.org/topic/m.13099505
And addresses from which you paid users for sign-ups and so on.
Choosing accounts from coinbase or any exchange won't be of any use as you don't own the private keys of those addresses.