In the docs.ton.org, we find:

There is a necessity for the synchronization of message routing and transaction execution. In other words, nodes in the network need a way to fix some 'point' in a multichain state and reach a consensus about that state. In TON, a special chain called MasterChain is used for that purpose.

Blocks of the MasterChain contain additional information (latest block hashes) about all other chains in the system, thus any observer unambiguously determines the state of all multichain systems at a single MasterChain block.

1. My question is, how does this work in practice? Since Layer 2's operation stack also has many issues to address, how is it handled in TON?

2. How is finality usually defined in TON?