Does Weverse Shop sell concert tickets?

Usually no. Tickets stay on Interpark, Melon, Ticketmaster, etc. Shop sells goods.

Is a POB guaranteed for every order?

Only when the listing states a guaranteed benefit. Random pools can miss a specific member.

Shopping · 위버스 샵 구매 가이드 (멤버십·POB·배송)

How to buy on Weverse Shop (membership, POB, shipping)

Log in with the same Weverse account that holds membership when a listing requires it.
POB (pre-order benefit) cards are store-pool random unless the listing says otherwise.
Customs and delivery times vary by destination; the Shop tracking page is the source of truth.