Steaming api How to know if somebody retweets?


I want to give bonus points to user to a user who tweets from my app. How do i know if user’s tweet is retweeted. Do i need to use streaming api ? Are there specifc steps which i need to follow.

And also, since there will be thousands of users tweeting, do i need to store tweet id of each user and track that tweet id in streming ap to see if any retweets?

For this to happen, do i need to create twitter app and users need to authenticate the app?