Cst law- query

Hello A dealer is registered under UP VAT and he Buys & Sells some food items in Delhi without taking goods to UP or other states. 1) Does he have to pay CST on buying goods from Delhi? 2) Does he have to pay CST on sales made in Delhi? 3) Can he claim benefit of C form while buying goods? 4) At what rates he has to pay tax, if he can't claim C form benefit, on both buying and selling? Thanks