OK. Look. I am really trying to help. I'll put the Disclaimer "but don't take my word for it".
I have a ticket for a WC game. Bought through the official FIFA System. Once you have been allocated a ticket, you apply online for a FIFA Fan ID with the ticket reference number. You have to supply passport details & upload a photo. Then a laminated photo ID is couriered from Russia. That laminate is effectively your Visa to enter Russia. It saves you going through the much more complicated process of applying for a conventional Visa. I have some "on the ground" info, from people who were in Volgograd, who I trust, who also tell me there are vigorous checks of the Fan ID in order to enter the Stadium.
I'm a Blagger. I'm normally wary of "you won't get in" scare stories. But, you'd better have that Heads Up. Sorry.