can there be a normal wallet that is equivalent to a multisig wallet? for a normal wallet : if you own the private key you own the money
can we say that the multisig wallet is just a normal wallet which the private key was derived from others wallets ?
the multisig wallet is just a normal wallet which the private key was derived from others wallets


That's pretty much exactly what it is. A multisig address lists the public keys that are allowed to spend the coins, and how many members of the group must sign (for instance, you can require 2 of 3 signatures). As long as enough private keys are accessible, the funds can be moved.