1. How did Monica know that Wanda nearly beat Thanos dolo? Was it ever documented? Or is that a plot hole?
I had this thought too while watching but it isn't a plot hole. There can be any number of explanations that could explain it, such as
1. Tony Stark recorded the entire encounter. It took place right outside the Avengers compound, so there is likely a ton of surveillance tools, like drones, at his disposal that could have been deployed. At minimum, there were a bunch of people there that have suits or goggles that record everything (Tony, Pepper, Rhodey, Sam, Peter, etc, in fact Peter probably uploaded his footage to Tiktok
)
2. Wakandans had planes/ships on the battlefield, and their systems could have picked up every inch of the area. They probably have holographic images of everything that happened.
3. There were thousands of individuals there. They likely reported what happened.
4. There isn't any reason journalist, scientist, and military weren't on the periphery of the battle, watching the entire thing play out from helicopters, planes, telescopes, binoculars, and their own drones. The Avengers facility is in NY and even if the general public didn't know where it was, there was a giant spaceship sitting in the air that any satellite would have picked up.
Remember that this was the battle for the fate of the galaxy. We have detailed wikipedia entries for historical conflicts and battles with less eyes on them than that. Half of earth disappeared and then reappeared. This is 9/11.WW1 and 2 level media and world government scrutiny times a million. Society at large would have devoted all resources to finding out what happened, as understanding what happened at minimum would be needed for society to begin to function again. There would be documentaries and 24/7 coverage of the the blip.