Time Travel is possible but only backwards. You can't travel forwads in time because there is no set state to the universe in the future, it is a mess of probabilities and possibiltiies. The past has been defined, so you can travel back into it.

Anastasia, Faye and I are the only humans in history to have the ability to travel in time. We could all travel back as far as we wanted to go, but it's like Back to the Future, if you change something in the past it could have an effect on the presents. So going back into time is very dangerous because it can alter the the path of time the universe actually took. You quickly end up in Back to Future paradoxes.

Anastasia, Faye and I wil travel through time but we'll only do it a limited amount of time and we'll do it in order to understand what was happening at that specific point in time. Eg, we will go back in order to understand what Ancient Egyptian culture was really like.

There is no point in trying to change reality by altering the past. The Architect and all the Angels in Heaven determine the path of the universe. We have limited amounts of freewill nesc for us to choose between good and evil, but the plan of the universe is pretty much mapped out at this point. If you were to go back and deviate from it, God would have to intervene to push history back onto the same path it was on before the time traveller interferred.

You can't go back in time and kill Mayer Rothschild to prevent Hitler from being born and thereby avert WWII. The past is not written in stone, but if you try and change it, God rewrites it back to the way it was. As humans we do not have the power to change the course of universe history. We are actors in God's play. We can rewrite our lines and change some decisions, but we can't change the plot of the story really.