It was from Bitcoin wallet. I have a feeling the copy of it might have been stolen and someone could have changed the password as my email back then got hacked and i didnt bother much afterward as someone did change the password as i had written jn the saved email.
Was it specifically Bitcoin Core? Do you have the address of your wallet that has funds? If you do you can check it on a block explorer and see it yourself if you got robbed.
I just want help how can i open it offline or will it open using my old password without connecting it to the network.
You can open it offline and get your private keys to import them to electrum. By stop syncing, or turning off your internet connection, you can click Help --> Debug Window --> Console.
That would work if you enter it on console:
dumpprivkey [ADDRESS_HERE]
You may also need to enter this before the above:
walletpassphrase "your password" 600