Regarding block validation in blockchain In mining process, miners validate the block based on proof of  work or using some other consensus mechanism.
Miners also validate the block. So in this validation process, miners validate only hash value of current block (or) they validate the entire transactions and then they validate the hash value of current block.
Please clarify this.
Full nodes validate everything. A miner must be running a full node. Not all full nodes are miners, but all miners are full nodes.

A full node validates everything in a block; it validates the transactions, it checks the block header is correct, and checks the Proof of Work is correct. So in the validation process, full nodes (and thus miners) will verify that the PoW is valid (hash of the block header is less than the target), that the block header is correct (contains the correct target, merkle root, etc.). Then they will check that each individual transaction spends UTXOs that exist, check that the scripts validate to true, and check that the output amounts are valid (less than or equal to the input amounts). They will also check that the coinbase transaction pays out the computed maximum payout for the block (subsidy + transaction fees).