How to get Videos on iPhone?

So I deleted some of my apps a while back to make space for something, and I think one of them might have been the starter app "videos". I tried looking it up in the app store but it's not there. I need it to transfer a downloaded video from my computer to my phone. Thanks. (BTW, if you know of an efficient way to transfer videos from computer to iPhone let me know.)

IPhone 7s power button stuck

Not sure if I should contact apple themselves about this, or go call my insurance.

The power button is stuck inward, so my fiancé can't turn it off. This wasn't a result of dropping or anything, it just happened. I googled it and noticed this happening to a lot of people. I don't have apple care, since we couldn't afford it. We do have another insurance but like I said, since this is a defect of the device should we just contact apple?

Apple headphones trouble?

My new apple headphones (the ones that come with the iPhone 7 with the new headphone jack) were caught on a door handle and yanked out of my ear. Ever since then, one headphone doesn't work anymore, is there any way I could fix this?

Is the motherboard on my IPhone 6 fried?

So I have an IPhone 6 and I recently had let it die because I wasn't going to use it for awhile. It must've gone completely flat because afterwards it wouldn't even show the dead battery screen. About 3 days after I put it to charge and it just went into the apple logo loop and won't hold any charge as when I unplug it it shuts off. Is the motherboard on my phone fried or is it a software issue?

My iPhone's screen is not working well?

I have an iPhone 5s (old ik) and once in a while the top half of my screen will not work and it will do weird stuff, like if i'm typing, it will type random letters and its really frustrating. The only way i can fix it is if i turn off my phone and I do not want to keep doing that because i feel like it is not good for the phone. Also, when i tap very hard on the top when it doesn't work, when i let go, there's like some sort of sound that makes it sound like my screen is coming off, i also do not have a screen protector on. And idea on what it could be?