Is it possible to just copy and paste the bitcoin code and run it as your own bitcoin/ crypto without it updating/ syncing to the current blockchain.
If this is possible would this produce the key to the genesis block? I am very curious why you'd see bitcoin spinoffs like BCH have different wallet formats than bitcoin.
Totally you can! Bitcoin source code is available publicly and it is under the MIT licensing. So you indeed can copy and use the source code and run your own shitcoin. But at the end of the day, it will probably be only you running network with no taker of your coin just like thousands other shitcoin in the market which no one really cares about!
Dor example, look at the ICO scene happened in 2017-18 period where people have lost millions.