[Ethereum] Mist wallet password test

If I understand your problem: You installed Mist and created wallet some time ago. Now you still have access to that installed Mist, but you are not sure if you remember the password. If I'm right try below:

Create another account in e.g. myetherwallet.com and try to send some Ether to that account from the Mist wallet.

Other (maybe a bit simpler way) is to run, this easy example Dapp in your Mist browser, when you will try to vote, Mist will request a password. If you succeed you will spend just pennies on gas. https://ethereum.github.io/stake-voice/

Yes you definetly had to provide a password when you created your account with mist.

Your keystore file contain your private key, but it is encrypted, and you need your password to unencrypt it. You can try to brute force your password with this tool:

https://github.com/burjorjee/pyethrecover