Graph Cliques

Friends. Two people are connected by an edge if they are friends. Find the largest group of mutual friends.

Strangers. Two people are connected by an edge if they are friends. Find the largest group of strangers.

Complement Graph. Connect vertices in the graph on the left, such that its complementary graph on the right has 4 vertices without any edges between them.

There is a pair of strangers among the selected people.
Try to find a larger group!