Fist of the North Star machine help

[Honda_CR-Z]

Hey guys. I am new to this world of Japanese games. I have always been attracted to them. Today I walked into a thrift store, and there in the back with all the other electronics was this Fist of the North Star machine...for $80. Of course I have a lot of questions. Please let me know if this is not the right spot to post. Pictures of the machine, board, and all stickers/branding in imgur album link below

IMGUR link to photo album of the machine. http://imgur.com/a/fLKrJ

#1. it has the configure (google translated the kanji) key, but does not turn. I'm guessing the keys got mixed up at some point and I have the wrong one.
#2. If that is the odds selctor key...and if it is the wrong one, I saw people selling new keys and tumblers on ebay. Would this be an easy fix?
#3. I was playing it for a while and now it seems to be stuck in the bonus game, which I read is normal and must be played to completion. Is this true?
#4. I cannot find the volume knobs....it is so damn loud lol.
#5. I believe the maker is Sammy Inc.
Sorry if my questions seem strange, or this isn't the right place to ask them. Im just excited to learn about this. I can also see this turning into a collection now. Once you get one...