I was just looking back at these and I thought I'd add answers and explanations- here they are:
The answer to the first is truth.
John Keats, in "Ode on a Grecian Urn," writes " Beauty is truth, truth beauty,' – that is all/ Ye know on earth, and all ye need to know." Go read it.
Pontius Pilate asked "What is truth?"
The last line is a reference to the common adage "The truth will set you free."
The answer to the second is time.
Some philosophers, in particular George Berkeley, believe that time is an illusion.
Time, like a river, is ever-changing, but it is measured always in minutes hours, and years.
"Time waits for no man" is a reference to the song by the Rolling Stones (yes, really)
And the popular expression "Time heals all wounds."