How to get product price from server to use in In App Purchase implementation?

We have an iOS app, in this app we want to integrate In App Purchase. I have gone through Apple docs about it.

I have some queries based on our iOS app's functionalities:

1. How to get Product Id with Price from server? The product and its price is not fixed. The product will be created from server with its price.

2. How to validate the product and its price from App Store?