Are There Universal Existential Truths?

Assuming that we know what truth is and how to find it, the question then arises, are there universal existential truths? In other words different people derive different ‘truths’ from same experience of reality. Some even have their own methods of deriving said ‘truths’ and are sure about those methods. How can we tell whether the truth which we derive or perceive is experienced in the exact way as all other conscious beings?

Secondly, what is reality? Something existing in the mind or in the world or both?