Digraph : A directed graph (or digraph) is a graph (that is a set of vertices connected by edges), where the edges have a direction associated with them.
Consider ablove graph now Assume E = S.
1. V1 and V2 that are simultaneously on function call stack at some point during DFS from vertex S then there exists a directed path from s to V1 and s to V2 . -> yes since when E and (DBC) on stack thier is directed path so yes path from V1 to V2 is there .since path from S to v1 is there so s to v2 also there so True.
2.V1 and V2 that are simultaneously on function call stack at some point during DFS from vertex S then there exists a directed path from V1 to V2 and a directed path from V2 to V1. -> Flase since If there is only directed path from V1-> V2 then need not be path from V2 -> V1. like here in image Path grom A to B is there but Not from B to A. ( When start with A , A and B on stack at same time.)
3..V1 and V2 that are simultaneously on function call stack at some point during DFS from vertex S then If there exists no directed path from V1 to V2 , then there exists a directed path from V2 to V1 . True since to be on stack simultaneously there should be directed path from A-B or B-A.