Yes. If you pay for 6 or 12 months right away, you will get 30% of 50% off respectively.
We have very reasonable prices. Most services charge more per month that we do for three.
No, we never use any prohibited techniques. We only use Instagram for authentication. Our service was approved by them when we were connecting the API. To do that, it was required to provide a screencast of the way the service works.
If you've changed your Instagram username, then you should press the "Install" button in your account again and after that you'll see the "Update information" button. If you press it, the system will get updated information from Instagram and ask you if you'd like to change the link.
One Instagram profile — one rate plan.