Apple Watch SE 2 (2022) with iPhone 7

That depends on which seller on Amazon you are buying from. There is an official Apple Store on Amazon. But if you are buying from a 3rd party seller, the warranty may already be used, even on a new watch as Apple Warranty starts the day the watch officially leaves Apple inventory. If a 3rd party seller got the watch a year ago and it's just been sitting on a shelf for a year, it would come with no warranty as it left Apple inventory a year ago.

Honestly, you are going about this backwards, in my humble opinion. I would highly recommend moving up to a newer, more modern iPhone, which can run iOS 16 and then buy an Apple Watch and you won't have any issues.

No you need an iphone that is running at least ios16 and that is an iphone 8 or higher.

Any watch running WatchOS8.7.

Or conversely to fieryjack's post above, no watches Apple currently sells.

Yes as long as it is running WatchOS8.7 or lower.

As long as it comes with a version of WatchOS 8 it will work with an iPhone 7.

You're welcome and good luck!