I don't use Tier 2, but the principle is the same.
You should try to create one main game loop. Within this, you can handle all of your levels with the same game logic.
Your scripts/logic should be rationalised so it can be handled in the same way for every level.
For example, take MuckyPaws' Manic Miner project. He has 40 levels, but one game loop. In a very simple format he:
Loads level from a text file. Each character in the file defines a space, solid block, eroding block, conveyor belt, key etc. He has a routine to read
any file and create the level.
From this point, everything works the same. If you press a key, Miner Willy walks. Every time he reaches a new block, the logic examines the block and makes the same decision for any level, for that block type. The decision might be walk (solid block), start eroding block, continue eroding block, fall, collect key, exit level.