iphone 6s with ios 9?

It can be updated but be careful about buying used phones.

iCloud: Activation Lock - http://support.apple.com/kb/HT201365 - This is a security feature, in part to deter re-selling of stolen devices.

Turn off Find My iPhone Activation Lock (formerly: Activation Lock: Removing a device from a previous owner’s account) - https://support.apple.com/HT201441 - If an activation lock was put on a device, only the owner of the account that applied the lock can remove it.

It probably means it's been sitting on a shelf for at least a year and a half. Based on that alone, I would avoid it. No telling what shape the battery is in. They don't like being stored without a charge for long periods of time.

If you are looking at an iPhone 6s that still has iOS 9 on it, then more than likely it is a gray market phone and won't have any warranty on it. It was purchased a while ago and the warranty begins when it is purchased. While they may say that it has not been activated, it doesn't matter. I wouldn't purchase a device except from Apple or an Authorized Apple reseller. While you could update the iOS on the device and you may not have any issues with it, if you do, then you won't be covered by warranty. I would steer clear of it.

And who is providing this warranty, I'll bet it isn't Apple. I never said it wasn't legal, what I said was it was a gray market phone. If they are not an Authorized Apple reseller, then they don't get their phones from Apple, but from another source, which means the phone is sold to them first, which is what activates the warranty. So even if it is in a sealed box, it isn't new, and probably doesn't have a warranty. No telling what region of the world that device was designed to be sold in either. Up to you if you wish to waste your money.

Legal does not mean authorized. If they are not an authorized distributor of iPhones, then it does not have an Apple warranty. Also, if they are not an authorized distributor, then it is not "new". Even if it's still factory sealed in the original box, as far as Apple is concerned, it's used.

Just like when you buy a new car. The minute it's titled, it's considered used, even if you haven't driven it off the lot yet.

Just because it says that, doesn't mean it is true. It is up to you what you do, since it is your money. We are just providing you with what is and isn't true from Apple. You make your decision based on whatever you wish to believe. However, I'd be awful disappointed if I purchased the device, found it was designed to be sold in Japan, the only place the warranty was valid was in Japan, and the warranty was expired because it was purchased more than 12 months ago.

Your money, do what you want.

wiki, as I read it, has the iPhone 6S in production. That doesn't mean it's being sold in your country. Apple continues to manufacture older models to be sold for less in certain countries.

That doesn't change anything. If they're not an authorize retailer for iPhones, then you will NOT have a warranty from Apple.