Like in the topic, PasswordHash - How to decode it?

The password hash is md5 encrypted and that's a one way encryption so it can't be decoded. If you lost your passwords you could write a program to crack it by md5 encrypting possible passwords and comparing them to the hash... or you could just change the password.

And I cannot view user pass by smth like TargetedUser.password ?

well, if you really need to have text passwords, put into your pol.cfg

RetainCleartextPasswords=1

After that, the account must be successfully logged into for the account's password to be put into accounts.txt.

And no, there is no way to get the actual text password from within game by a reference. The only closest things are:

who.acct.checkpassword(pass) where pass is what you think the password is. It will return true or false if that was correct.

and

who.acct.setpassword(pass) where pass is what you're changing the password to.