How long does it usually take to transit for a flight from Daegu KR via Pudong to Singapore?

It takes about 2 hours. You needn't claim your luggage, and your luggage will be checked through to the final destination. Upon landing, you need to confirm your onward boarding pass. Next, check in, and go through quarantine, immigration, and security check. Then, wait and board. By the way, China Eastern staff will help you make the transfer. It is less likely that you will be forced into buying a new ticket. Don't worry!