Projects cost increase how does one claim for increased cost? In commercial and Techno commercial terms?

As variation Orders contractor has to Submit CRVO.

Ability to claim depends on the type of contract and the contractual terms. You have to read your contract and review all the clauses carefully and also to know the implied terms of the contract (laws which govern contracts in the contract's jurisdiction which are implicitly part of the contract even though not expressly written into it), and only then can you determine if there is any solid basis for a claim, and how to make the claim.