How long was the iPhone made for?

iPhone can be useful for three to five years, and variously longer.

I have an iPhone first-generation around that still powers up though the telephone network support is outdated and the iPhoneOS software are all long gone, and have a working iPhone 6s that's used for testing. Wouldn't tend to use the 6s now as the newer iPhone models are seriously faster, and much more capable.

An iPhone 6s is pretty old, and is the oldest supported by the current iOS software.

Various problems can arise, including with your iPhone battery. (Apple offers a battery replacement service.)

Errors or diagnostics or symptoms can potentially help target answers to your questions.

What apple? You will need to be more specific. And get read for a ton of spam to your email address.

Ok, but to help you with that we need much more information, what is happening that it doesn't work, any error messages, when did it start, etc.