Are Tx process parallel? How are the account data guaranteed not overrided each other by simultaneous Tx?

Question

As stated in title.

Does runtime sort all input account an add mutex-locker to those accounts that are mutable?

Answer 1

Anatoly explains the Sealevel runtime in this blog article: https://medium.com/solana-labs/sealevel-parallel-processing-thousands-of-smart-contracts-d814b378192

TL;DR: All transactions must specify in advance which accounts are writable. All transactions that do not write in the same piece of state can be processed in parallel.