Is it paved the whole way?

Yes, paved the entire 4.25mi

Yed

Yes, the trail is tarmac but it is still closed. Fine for walking when it's open.

Before the Montgomery building renovation; it was paved but warped. The trail was uncomfortable and unpleasant to ride on a road 'fitness' bike. It's better for a mountain bike or running.

I believe it is, tarmac end to end but I have not been to the Windsor Locks portion. I don't think it has been reopened, because of liability concerns due to renovations in Windsor Locks.