What is the significance of the game of questions to the action of the characters / existentialist meaning of Stoppard's play?

From Rosencrantz and Guildenstern Are Dead Act I

Rosencrantz and Guildenstern were interested in knowing what happened to their friend hamlet who has been misbehaving. They tried asking questions from him but were confused. Guildenstern suggested to Rosenvrantz that they should change identity so that they can practise the question answer game. The game had no significance as they became more confused. Hamlet had an valid reason for been angry because he just lost his father and his uncle misbehaves.

While still on stage Hamlet came in and confuse his friend colonius for a riddles they become more confused.