hello everyone.. Instead cold storage a lockdown mode address or Frozen Storage address could be added to bitcoin?
I don't know what lockdown mode or frozen storage address, and it probably exist only in your imagination.
Attacker might able to steal private key after user make a transaction from special address,but how do you plan to prevent this accident?
Private key can never be stolen from any transactions you are making.
Best way to protect your private key or seed words is to keep it offline, written on paper or on metal, and adding passphrase would be best simple protection.
Multisig setup is much more safe but it adds complexity and it's not foe crypto newbies.
How do someone veto a transaction which made by attacker where we can verify who's the owner or attacker without compromise owner privacy?
There is easy way to sign a message with Electrum or other wallets to confirm you are the original owner, but there is no way to ''veto'' transaction, whatever that is.
Identity of person who signed a message is safe and not revelead.
Assuming a transaction is reversed, that means blocks would become invalid since it's hash (along with all next blocks) will become invalid? How do you plan to solve this problem?
There is no problem to solve here, and transaction in bitcoin can not be reversed.