African Side Neck Turtles

I recently adopted an African Side Neck turtle, and I have a couple of questions:
   
1. Should I put aquarium sand on the bottom of his tank for him to dig into?
   
2. Should he only be fed once a day and if he is full, will he stop eating?
   
3. Should I acquire anothet African Side Neck so he won't be lonely?
   
Thank you.