Please, confirm my current understanding of how futures work. Let’s consider cash-settled futures for simplicity.
The number of futures contracts (with identical parameters) is unlimited. New futures contract will be created by the exchange as long as there is a matching buyer and seller.
Any person can sell a futures contract - one does’t have to own it first.
If you own a contract you can sell it on the exchange. For other exchange players it will be completely opaque whether it is a newly created futures contract (created by the exchange) or an existing one, sold by its owner.