Can I create the backend projects on React native as a mobile app?

I’ve been doing mobile apps for sometime now, so I was hoping maybe if I could create the freecodecamp backend projects using Node and Mobile app so I could get more practice in mobile development. Is it acceptable or creating a website is the requirement?

I don’t see why not. If that is what you want to do.

It might be better for you to get some experience working with mobile development in companies which specialize in this area such as
https://itmaster-soft.com
https://clearbridgemobile.com/services/
And Node is rather not suitable for creating mobile apps.The mobile piece of your app, the one you would download to a phone, tablet, etc is built with any number of options.