From I and II:
C is sitting second to the left of G. C is sitting third to the right of E. G is sitting second to the left of H.

F is sitting second to the right of E. H is sitting to the immediate right of B. A is sitting to the immediate left of F. D is sitting second to the left of B.

So, H and E are sitting at the corners. So, statement I and II are sufficient together.
From II and III:
Three persons are sitting in between B and F. D is sitting second to the left of B.

C is sitting third to the right of E. B is not a neighbour of E.

H is sitting second to the right of G. A is towards the left of D. So, case 1 is invalid.

So, H and E are sitting at the corners. So, statement II and III are sufficient together.
From I and III:
E is sitting third to the left of C. C is sitting second to the left of G. F is sitting second to the right of E.

H is sitting to the immediate right of B. H is sitting second to the right of G

A is not a neighbour of C or G. D is sitting second to the left of B.

So, H and E are sitting at the corners. So, statement I and II are sufficient together.
Hence, any two of the three statements are sufficient together.