Will my iPhone 4s still work after 6 years of not working?

You can get a replacement battery, but the phone will still not work as a phone; if you have Wi-Fi you may be able to use it as an iPod Touch. But there’s a good chance it won’t work at all, so spending money on a battery replacement is not a good investment. You have an 11 year old device; that’s well past it’s useful life.

If you live in the US, there would really be no reason to even try to get an iPhone 4s working. If it's been powered off all this time the battery has likely died as well. iPhone 4s is a 3g phone. And 3g is already shut down by most providers and will be completely shut down in the US soon. That means it won't be able to operate as a phone at all. And at this point, an iPhone 4s is considered obsolete and there would be no support available from Apple for such an old, out of date device.

Appleuser123– wrote:

Then couldn’t I get a new battery for it I know some stores that sell those still my friend has got another battery from the seller as well and also so I can’t connect it to the internet at all?

Apple wouldn't provide a new battery. I don't believe they did that until the iPhone 5. Battery replacements were just processed as complete replacements. They still list the 4s as having replacement service, but that wouldn't include anything where the contents would be recoverable. The assumption would be that it was properly backed up and then the contents could be transferred to a replacement.

If the contents are important enough, you might take it to a third-party repair shop. If it's been stashed away for up to 6 years, I can almost guarantee that the battery is in deep discharge. But hopefully the rest is intact. I wouldn't anticipate that the device itself would suffer from flash memory endurance (fading) issues after 6 years of storage, but that's a possibility. They could see if it's in working condition, whether that's by plugging it in to external power or maybe using a known, working battery. It might be worth it to consider a new battery if the service is cheap enough and you just want to take it home to just retrieve the photos and video.

If it is working, the important thing would be that they have the passcode. If your mom forgot the passcode, then it's not worth trying since it's unlikely that it can be cracked.

Lawrence beat me to the punch. But his assessment is spot on and it would simply be a waste of good money to try to get this device working at all.