Is it possible to know the truth without challenging it first?

I concur, Is there such a thing as 'absolute' truth?

It's impossible to be certain of any truth even if you challenge it.

Good question....not really..but once you know something you then can apply what you know to similiar situations...

No way. You have to test it, or else it's called "faith"

if you know the Truth it will set you Free so you wont have to question it, so what do you really know

Some truths can be known based on observation and without challenge. Of course, I am defining "truth" as something which is based in current known "natural laws". Fall from a high distance without anything to slow you.. You'll most likely die. That is true.

i dont know i like to get all my facts in order to acknowledging something as true

Untested beliefs might be true.

yes.