Yes, it can play while charging. 

It takes approximately 3 to 4 hours to fully charge the Turtlebox from 0% to 100%. 

Yes, on  Gen 1.5  and Gen 2 Turtleboxes there is a 5-step battery level indicator that shows the current battery life in 20% increments.   It works similar ...

At full volume, you will get 6+ hours of playing time. At 50% volume, you can play for days!