Can I trade in my partially paid iPhone for a new one?

I agree with varjak paw. Depending on who you financed the phone with, they will very likely require that you pay off what you owe before you can trade it for a new iPhone. Think about it. You took on a debt and most creditors won't release you from that debt until it is paid in full.

First, however, you should check with whoever financed your iPhone. They will probably require you to pay any remaining balance before you can trade in that phone.

Yes.

It depends on what you buy and how you pay for it.

If you buy an iPhone, iPad, Mac, or Apple Watch and pay in full, they’ll apply a credit to your original payment method up to the total purchase price. For any remaining amount, you’ll receive an Apple Store Gift Card via email.

If you buy an iPhone using Apple iPhone Payments and include a trade-in, your estimated trade-in credit will be applied directly to the purchase price of your new iPhone. Once they receive your trade-in device and confirm that the condition matches what you described, there’s nothing more you need to do. If it doesn’t match, your original payment method will be charged the difference in value. In that case, they’ll work with you to confirm that you still want to move forward with the trade-in.