Everything should be automatic and you would only unlock the lid when the whole process is finished. You shouldn't have to manually let out the steam, it should have been released automatically near the end of the cooking process. Are you trying to unlock the lid before the rice is finished cooking? Then I could see how you would have to release the steam manually. Otherwise, your machine may be defective?

Yes, this is perfectly normal. The pressure is locking the lid on the Cuckoo. You have to reduce the pressure inside the Cuckoo by letting ALL the steam through the valve before you can open/unlock the lid.