Has anyone played Sound Voltex Booth before?

I am new to playing the game, however I've been aware of the series for 3-4 years, and I have some questions:

- The arcade I visited uses QR codes to store data, how common is this among the "Booth" cabinets?

- Is the game still prevalent in certain countries or regions?

- Is there a time limit difference between playing as a "guest" and using an account to play the game? Because, the first time I played the game, I didn't have a Konami account, and according to the cabinet sticker, I need to insert 3 tokens. It lasts 2-3 songs, however I did try only inserting 2, and it only lasted me 1 song. I played with an account in my 2nd visit, after logging in, the game tells me that I only need 2 credits (tokens) to play, and it also lasted me 2-3 songs.

- How come the credits that are accounted from the inserted tokens doesn't completely deplete(when playing as a guest)? I insert 3 tokens as the sticker suggests, and after my session finishes, there would be 1 credit left. I would play another session, inserting another 3, and after finishing that session, it would stack up to 2 credits. Is this a bug or could I play another session even without inserting in more tokens?

This is my first time playing on an arcade in almost a decade, the last time I played one was during my childhood.