Get the engine and some assets. Write your game. Sell it on Steam or the Epic games store ( or anywhere else you fancy ).
That’s a business thing and nothing to do with the game development process. You don’t have to use a business name.
You can put a copyright notice in your game credits or wherever, but once it’s out in the world, it will be quite obvious you wrote it before the person copying you did.
The whole point of asset store items is that you can make a game with them, you don’t have to pay any more for the assets after initially getting them. But, if you start making stacks of cash out of your game, then you have to tell Epic, and start paying them a percentage - see the marketplace faq: