A relatively simple way scientists date things is by using carbon dating. Now, this is only accurate a few hundred years either side, due to the nature of carbon dating. However, by any more than ~200 years is not really going to happen. We just have too much evidence.

The stonework has been proven to be actually pretty easy with the simple tools they built, it just took a lot of slaves to build it.

And it's unlikely, just due to the sheer amount of evidence we have, from a fossil record if you mean that much older, to built structures, or lack thereof.

Theoretically, maybe? The biggest problem with that is that you can't physically get faster than that, even theoretically