Can I restore my account without seed and wallet file, using just the keys file? and do I need to know the password if you can restore from key file?
You DO need your password (which may be empty if you did not set one originally) to use your keys file. The keys file itself is encrypted by a key derived from your password.
If you do not have your seed, and lose your password, the keys file will be useless (unless you can brute force the password).
For the interests of clarity, "restoring" from a keys file is the same as "refreshing the wallet from the first block, rather than last refreshed block". They keys file is needed for both, and the wallet behavior is the same (except the refresh starting point is different). This may help see why your password is needed, since you input it when you open your wallet.
As explained here you can restore from keys.
You do need a password to decrypt your keys file in order to use it to restore your account
Making a very strong password is essential to properly protect your encrypted keys file so that a hacker cannot read it. Make your password long and random.