I'm a student looking a develop a user-friendly educational map of Mars. I know a good deal about GIS at this point, but only just starting to get into the development side of things. Esri has their story map, which as I read they will host as well. They also allow developers to download the code off Github and customize it to their liking.
1. How much data will ESRI host?
2. Is story map only compatible with certain map projections? Or any unusual limitations I should be aware of?
2. If I should go in and customize the UI to fit my needs can it still be hosted by ESRI?