Sounds a bit fishy. Phones seem very under-powered to mine crypto. Not to sure why you want us to enter your username as the code, unless it's a pyramid scheme.
Couple that with most people having their whole lives on their phone, and it sounds like an easy trick to get people to download an app that will open a network connection that allows uploading of personal data without their consent, or without their knowledge. Opening the app once a day to "prove you aren't a bot" sounds more like, "open the app daily to make sure your phone settings haven't put the app to sleep".
Do not trust.