"I've been everywhere and seen everything and done everything." - The present perfect is a retrospective tense. It expresses the idea 'before now'. It is a present tense. Something in the moment of speaking is making the past actions feel psychologically immediate to the speaker. The sentence suggests "I've been everywhere and seen everything and done everything AND THAT IS WHY I FEEL SO TERRIBLY BORED RIGHT NOW." "I was everywhere and saw everything and did everything." - This verb form expresses distance in time (the past) and psychological distance. The past actions feel more distant to the speaker at the moment of speaking. There is no implication of a present effect.

They are quite odd sentences! To me, the first one is very general, and therefore probably a huge exaggeration or a lie! It means literally everything, and everywhere. If the person has been to Antarctica, Syria, Sierra Leone and Columbia it might be true... The second one is a little odd. Normally, we would say 'I went everywhere'. But, given that, this would be appropriate for a limited context. A child might say it when they came out of an adventure park. It means that they went everywhere, and did and saw everything at that place.

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