How to create a cold bitcoin wallet?

Question

bitcoin

Good afternoon.
The goal is to create a cold bitcoin wallet to protect money.
I looked at different instructions, please correct me if something is wrong and answer a couple of questions:
1. Through electrum / bitcoin-core I create a wallet WITHOUT Internet on an offline machine
2. I copy all bitcoin addresses from the wallet to receive money on them and transfer to an online machine
3. Copy the xpub-key for the watch-only wallet to the online PC
Questions:
1. Do I need to be online at least ONCE in order for the wallet to be created? Or is it done offline?
2. How to create new addresses for receiving money in an offline wallet? Using the example of an electrum or a standard wallet
3. The public key, when entered on the online machine, shows which addresses? ALL that were created before? And if I create a new wallet, will the public key change? (otherwise how to transfer new recipient addresses to the "view-only" wallet?)
thanks

Answer 1

The most important thing was missed.
After creating a wallet, encrypt it, and make a bunch of geographically separated backups.
It is not necessary to transfer keys, all transactions are visible in the blockchain. You only need to know the wallet addresses.
Key pairs are generated offline, are not synchronized with anything and do not depend on anything.
New addresses in wallets are created by regular means on the tab for receiving payments. I recommend generating more of them right away so that there is a reserve for various unforeseen needs.

Answer 2

1) Not necessary.
2-3) Each address has its own pair of keys.

Answer 3

Here is the English manual.