Do you believe in cold wallet If yes, which will you recommend? If no, why not?

Not your keys not your coins

You can use a hardware wallet as a cold wallet too. Simply initialize it, then safe keep the mnemonic somewhere safe, preferably it on a piece of paper, and in a safe box that cannot be easily removed (safe box that are small are almost useless and NOT safe).

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My preference is to keep it in a digital safe that is not connected to the Internet, in a computer vault with multiple layers of encryption (and methods). There are advanced ways to use hardware (cold) wallets and encryption methods that are quantum computer resistant which I cannot reveal here.