Is altering Blockchain Wallet possible even after all the securities?
The key thing to learn is that a scammer doesn't need to alter your wallet. They don't even need your wallet to exist, they can access money that was in a wallet that has even been deleted.
The minute I fund the wallet, he took all the money out even after all the securities on my wallet. How is this possible?
Bitcoin wallets don't contain any Bitcoin really. What they contain is a private-key that gives you the right to spend any Bitcoins that have been sent to a Bitcoin-address that is derived from that private-key.
The money is effectively stored in the blockchain, every "full-node" bitcoin wallet has their own full copy of the blockchain. Any wallet can spend money if they can prove they have the private-key for the bitcoin-address associated with the Bitcoin.
You can prove you own a private-key without disclosing it. That's the mathematical feature that makes Bitcoin possible.
The wallet-password or two-factor authentication only protects access to your copy of a wallet. By earlier giving someone temporary access to your wallet, they can copy from the wallet the private keys (or seed-phrase/recovery-phrase) that they can use to create another copy of the wallet.
Even if you change the password on your wallet, that doesn't affect other copies of the wallet.
If you put money into your copy of the wallet, that money appears in all copies of the wallet which contain the same private key. It doen't even matter if the copy was created before or after you put the money into your wallet.
Any of those wallets can spend the money you put in there. Once one wallet has spent the money, it disappears from all other wallets too.
You may think that calling this thing a "wallet" is misleading since it really contains no money. I'd agree. The inventors of Bitcoin needed a familiar name for a thing that controls access to money, that was the best they could come up with.
Maybe it is best to think of a wallet as a combined key-holder and accounting-ledger viewer.
So never share access to your wallet, even if it is empty at the time.