You can't prove there aren't more dimensions. After all you could be hiding them in your garage with your invisible dragon or you could of rolled them up in a Calabi-Yau manifold.
Time is a unidirectional so it's considered to be a different kind of dimension than the spacial (bidirectional) dimensions.
.. Although depending on the particle theory you subscribe to, it may only be unidirectional to us (positrons being electrons moving backwards in time, etc.)
Time is a unidirectional so it's considered to be a different kind of dimension than the spacial (bidirectional) dimensions.