When will the Hindi for English speakers course be available on the android Duo app?
It varies greatly. Some have come out on all three platforms on the same day (one of the far Asian languages did this, maybe Korean or Chinese?), while others are web then mobile, with the mobile rollouts either separate or together. I believe some courses have even been released mobile before web (again an Asian language, possibly Japanese on iOS first?).
Generally speaking however, the course is almost always available on mobile before it graduates from beta. Graduating beta simply means the number of reported errors in the words, pictures and sentences have dropped enough to consider the course "stable" from a language standpoint. Beta status doesn't really have anything to do with the backend programming per se.
You sir are awesome! That gave me the peace of mind I wanted. I have been waiting for Hindi course almost 2 years now and I was so excited when I looked online and it was ready. I went to the app and it wasn't there. For now, I'm using on my computer and mobile browser on tablet.