My question here is, the way Bitcoin wallets are programed and being generated, is it also certain that old unused Bitcoin addresses (that was generated by someone but was not used or probably lost his phrase) can never be recycled by the system to be used again?
Nobody can act as your SIM provider in a decentralized network. Bitcoin addresses don't expire. They don't get recycled either. Just because someone lost his private key, it doesn't let the network magically gains access to it. There are about
2^96 other keys that can create a valid signature for that specific address either way.
Furthermore, there is no need for recycling. The number of private keys is stupidly big.