What are the height or age requirements for Loop-Dee Doop-Dee?

The minimum height is 92 cm. With an adult, the minimum height is 122 cm. The maximum height is 190 cm.

How do queues or reservations work for Loop-Dee Doop-Dee?

Paid standby/express is offered.

Loop-Dee Doop-Dee at Universal Studios Beijing News | Thrillspace