Why can't I update Instagram?

I don't have the feature where I can switch between accounts more easily. I know some people have it and others don't, but I have an iPhone 5s and it won't let me update it? Is my phone too old or something?

IPhone 5 troubleshooting

My iPhone 5 keeps shutting off unexpectedly and everytime i text it texts by itself and scrolls through emojis. I factory resetted it, but still seemed to not work.

What do you call this type of photograph?

I love these types of pictures, but sadly, I don't know where to find them, because I don't know what they re called. They re pretty difficult to come across. It's when you hold a photograph (such as a polaroid) up in front of the place where you originally took the photograph, and you take a picture of that moment on another camera.
Another thing is taking a picture of iphones taking a picture. I LOVE this. IIm attaching some examples below, because I know it's hard to explain. Hopefully someone knows a good word for this.
http://streetiphoneography.com/post/136126969095/line-up
http://www.samalive.co/through-the-phone/

Added (1). Searching "picture of iphone taking a picture" brings up the best results, but it sounds so lame. It really does deserve a more majestic title. Like me.

Why does my Verizon IPhone 6 go straight to voicemail?

I got an iPhone 6 in the summer and for the past month or so, when someone calls me, my phone goes straight to voicemail. I've tried resetting my phone, making sure Do Not Disturb is off, clearing my voicemail, and I've had no success. Is there anything I haven't tried?