Does registration cost money?

Usually no — the ticket purchase later does. Beware third sites charging “registration fees”.

Can one household use multiple codes?

Platform rules vary; coordinated multi-account abuse can get orders cancelled.

Tickets · Ticketmaster Verified Fan — K-pop 등록 창구 이해

K-POP向けTicketmaster Verified Fan

Registration closes on a published date — late signups usually do not receive a code.
A code does not stack with every venue partner presale; read which inventory it unlocks.
Weverse / global fan-club membership is a separate product; some tours use both in sequence.
If you never receive email, check spam and the Ticketmaster account message center before assuming rejection.