Do apps update if I update my iPhone?

I know it's a bit of a stupid thing to ask, but I completely forget. I really need to update my iPhone, but I don't want a few of the apps to update with it

Does iPhone 6 useable and not obsolete in 2017 and with the newest version of ios?

I watch a video on youtube about this guy saying that don't buy iPhone 6 because it become slow because this new version of iOS 11. Does it true because I want to buy this phone.FYI, i'm cheap but I want to use an iPhone so badly. I have enough money to buy iPhone 5s but I don't want to use a small screen phone.so I want iPhone 6 but also my money is enough just for 16gb version so I waiting for my money to be enough to buy 128gb version. I want your opinion what should I do. Does it become so slow, I can handle slow and hang because I use a very cheap smartphone right now and it always hang. Can I not update iPhone 6 and use iOS 10. What would happen?

My iPhone 6 camera sucks

Tonight there's a beautiful orange full moon and I have a love for photography. I can't find our professional camera so I'm stuck with my iPhone 6. When the back-facing camera focuses, it just shows a ball of light. It could be from a street lamp for all I know. Which model iPhone or just phone takes the highest quality photos? Because I know for a fact mine doesn't!

How much would an iPhone 6s with no data cost?

I can't find any straight answers on the Apple site or anything. I'm from Manitoba Canada so I'd be going with a no data plan from bell MTS and I don't know if the gb would Effect the plan, but I'd want to get an iPhone 6s with 32- 128 gb. Does anyone know how much this would cost?