Yes, You can validate the chain through the merkle root.

https://medium.com/coinmonks/how-to-manually-verify-the-merkle-root-of-a-bitcoin-block-command-line-7881397d4db1

https://stackoverflow.com/questions/52896276/how-can-merkle-trees-help-validate-the-content-of-a-block-in-a-blockchain

I don’t have to confirm answer for the 2nd question. I think that's the case and also smart contract data too. Need to research about it.