Is Interpark Global used for European tour dates?

Rarely. European legs are sold on local promoter platforms. Interpark Global is mainly for Korea (and some Asia) inventory.

Where do I find the fan-sale code?

Usually in the artist or promoter email, or inside the paid fan-club portal named in the tour notice.

チケット · 유럽 K-pop 콘서트 예매 (Eventim·Ticketmaster·Fnac)

欧州は現地プロモーター販売。EventimやTicketmasterなど。

Join the artist newsletter and the promoter mailing list when both exist.
UK venues often push official resale; avoid third-party screenshots of QR codes.
ID at the door follows the venue country — passport or EU ID is typical for name-checked tickets.