I do not believe the fundamental nature of reality has changed since it started. Of course, I was not there to witness it. But I do not need to be there. I can infer from my experience of reality.

Firstly, the nature of reality had not changed from the beginning of my experience up to now. Tennis balls still behave the same way they did when I first learnt the game (taking into account tweaking of ball, racquet and surface material, etc).

I can infer that reality had not changed also from my parent’s time. They would have said something. Or else they did not notice. But that is doubtful. Someone would have noted this and wrote about it. Likely really had not changed and will committing to be consistent into the future.

The physical reality this can be taken to be reliable. It can also be taken to be the underlying reality with nothing beneath it. That is, we can ignore metaphysics. If metaphysics is constant, it can be safely ignored. We can and should concentrate on the physical reality, because it is the physics which would allow me to win a tennis match, and not the underlying metaphysics.