Private Memo Key: This key is used when transferring funds. In case of transferring steem, you will see a place where memo is required.

You have to edit this because it's not the function of this key, you use it for encryption and decryption of private messages.

I also have steemit public keys . Which are not required for login for example my Posting Public key, Active Public key, Memo Public key.

No dear there's nothing like this, the only public keys we have is that of our Tron wallet, that one is open for all to see. Others are private.

Step 1: Log in to your Steem wallet using an active key.

Wrong, you don't log in to your wallet with this key but the posting key. You use this key to validate transactions.

Then the master password is most powerful key, it can use to generate every other keys including itself. So someone can claim your account if they have access to it, keep it safe.