My iPhone won't allow my social media to post pictures

When I go on Instagram it says, "Please allow acces to your photos. This allows Instagram to save photos to your camera roll." It takes me to settings but it does not show anything for me to acces my photos.

I then went to Privacy-> Photos. It said "Photos stored on your iPhone may contain other information, such as when and where the photo was taken. Apps that have requested access to your photos will appear here." I've waited for minutes but no apps appeared!

ITunes Delete Multiple Songs?

How do I select a multiple amount of songs from iTunes to delete rather than individually?
( preferred method on iPhone )

Aftering using online check in for my airline, am I all good to go?

I'm flying WOW air. I notice they have a 24 hour online check in, and it will give me my boarding pass immediately which I can store onto my iPhone via the Wallet app

I have one checked luggage and personal item, do I still need to have these serviced at a counter?

And what of my e-boarding pass, do I just give them my phone to scan it or do I need to print something out?

My iPhone 4s is glitching?

My phone was fine one minute then I tried to use it and all the sudden the screen was messed up. It keeps flickering and the colors are kind of distorted. Whenever I change apps, its like half the screen has a fade affect on it and it takes a couple seconds to catch up to the other half. It works perfectly fine, though. I've tried turning it off and on, but that doesn't seem to help. I don't have the money to get a new phone either… Can anyone help?

How large I can print photos taken by an iPhone?

Recently I have started a photographic project using an iPhone 5s, which has a 8mp camera and I'm shooting this project on phone's built in square format. I'm kinda concerned whether I can print these photos in large size for any exhibition or photobook. I've checked the exif of those photos, it shows these photos have 2448*2448 pixels on 72dpi. Is this enough for large print? Can I have life size prints of these photos?

What's the best iPhone 7 Plus case?

Pretend that money isn't an issue. I'm looking for the best iPhone 7 plus case. Screen protector is a must (I know some cases don't have screen protectors). Also I don't mind if the case makes it bulky.