If timed correctly, you will enter the locked world. Beating the first stage of that world will keep it permanently unlocked.
If you are looking to unlock the full version of Angry Birds Seasons, here is everything you need to know about how these codes worked and the state of the game today. The History of Unlock Codes angry birds seasons unlock code full
Angry Birds Seasons was a major hit for Rovio, taking the classic bird-flinging gameplay and adding themed levels based on holidays like Christmas, Halloween, and Valentine's Day. While the game moved to a free-to-play model later in its life, many legacy PC and older mobile versions required an activation key or "unlock code" to access the full experience. If timed correctly, you will enter the locked world
Most modern versions of the game are "Angry Birds Friends" or the "Remastered" versions found on Apple Arcade, which do not use the old code system. How to Access Full Content Today The History of Unlock Codes Angry Birds Seasons