I want to purchase a iPhone 12 Max. When it comes out. I want to pay in monthly installments. I don't need 10,000 worth of credit. can I get 2000 dollars with of credit

Why would you not want to have a larger credit limit? Unless you have a compulsion to buy things and can't control yourself a larger credit limit is generally a good thing to have.

The credit limit is not something you need to use if you don't want to use it. Its a a max amount you can charge to the card at any one time.

There is nothing that says you need to spend it all nor do you need to pay extra for having a larger credit limit.

You only pay for what you actually spend on the card. If you have a $5000 limit and you only spend 1000 on an iPhone then you only spent $1000 on an iPhone. The other 4000 do nothing other than being available if you want to use them for something else at the same time you are paying your monthly fee for the iPhone. Once you complete the iPhone payments, that $1000 is again available for you to use for something else. The credit limit is not money you have and need to pay back, its just a maximum amount you can charge to the card at any one time should you want to.

Yes, you can cancel the card at any time if you no longer want it.

You can request to close the account at any time.

If you are wanting to get the Apple Card then it will just approve you for the amount you qualify for. At this point there isn't a way to ask for a specific amount. If you want to apply for credit in the store then you can do that and if you qualify they just give you the amount of credit you need for the transaction.