Iphone 5 instagram won't link with facebook?

Just got an iphone 5 and my instagram won't connect with my facebook. I get instructions from the iphone - Settings>Privacy>Facebook and to turn that on. That is turned on though and it still won't work. I don't know what to do, any help would be great am I missing something?

Apps downloading to both iphones?

So my sister will download an app to her phone, but then it will automatically download on my phone. We both have iPhone 5s. How do we stop this? I only want the apps she downloads to be on her phone.

Parental iMessage Monitoring?

I want to text my friend from Canada, who has an iPhone, but I don't want to explain having international friends to my mom, because that would lead to telling her about my blog and I don't want that either. Will she see that I've texted someone from Canada on the phone bill if I use iMessage? Or will it show up at all?

How to change the service of an iPhone?

My friend is giving me his iPhone 4S but he has AT&T and I have Verizon I know you have to change the SIM card but what if his service is still working? Does he have to call and tell them he no longer has the iPhone or can I just somehow change the service over to verizon my self? I'm new at all this technical stuff. I want to move a iPhone over from AT&T to Verizon even if the cell phone is still in use? Can I do that? Please respond!

Added (1). I would be using the Verizon 4G SIM card for the iPhone

Why don't email alerts show on my iPhone?

I just set up my phone yesterday do I'm new to it. Basically I logged into my Gmail account on the Mail app but for some reason new emails only appear when I go into the app and refresh the page manually. My mum has an iPod touch so I know that you can get them. I went into settings > notifications > mail and changed it so that the alerts should appear but they don't… It's an iPhone 4S if that helps.

Iphone lost/stolen can they use it?

I lost my iphone 4 days ago and no one has handed it in so someone has probably taken it for themselves. I didn't want to miss out on Christmas messages so I canceled the sim 3 days ago and the carrier (3 UK) told me they were going to block the phone too but that I could ring back and get it unblocked if I found the phone.

Firstly I had my own pin code on the phone so they could not use it when they found it, but then the next day 3 blocked the phone so my question is; can the person who has my phone now do anything with it? If they get it unlocked/jail-broken will it work even though the IMEI is blocked?

And second question; If they can unblock it will they be able to see all my photots?

Is buying the iPhone 5 contract free worth the money?

How does it work and what are the pros and cons? If you buy one contract free do you still get Wi-Fi and 4g? I'm thinking about buying one contract free because I have another smartphone with a 2 year contract.