Well, the dynamics of time are complicated, see we could never go into the future because we haven’t created it yet, however it’s likely we could go into the past. What we think would happen is if we were to go into the past there’s a possibility of changing our current future. So until more research is done, we’ve decided not to mess with it for the time being.
Again, much about time and what “type” of time it could be is still unknown, it’s a dangerous thing to mess with, we already know other dimensions exist so alternate realities is a definite possibility