Can i grow berries? If not can I stockpile supply of Rindo Berries in more reliable way than getting them randomly in Utira town once per day?
Unfortunately, you can’t grow berries, and you can’t buy them at the battle frontier. 
Actually you can buy them at the Battle Frontier. These two girls sell berries in the Challenge Championship building:
Wait, both of them sell berries?
I need to start talking to more people…