Slight corrections to the previous answers. The max allowed indicated airpseed is 250 kts. below 10,000 feet, all airspace. Same rule all over the world as far as I’ve ever seen. Some countries allow the controllers to waive this but not in the US. (kinda fun to drive up to the outer marker at 300, but that’s another story). 250 IAS will get you about 280 TAS at 10,000 ft., depending on temperature, then apply the headwind/tailwind to get the ground speed seen by the ATC radar and forwarded here.
There was a test of waiving the speed on climb out years ago, but it was dropped when aircraft were driving out of the side of the TCA (class B nowadays) instead of the top when they should have been at or above 10,000 anyway.
The altitude anomaly has been around for years, ever since encoding altimeters anyway. I once had an avionics guy try to use plain English to explain why. Something to do with the difference in the output signal between, say, 5000 feet and 5100 feet being pretty small. Throw in the other usual electrical stuff and it’s a miracle we don’t fall out of the sky.
Once in a while you will see an airplane that has just become airborne showing the cruise altitude that is filed in the flight plan, again that is something that shows up for one or two sweeps of the radar and is updated with the actual altitude as soon as the computer gets a full report from the transponder and processes it. Since FA does not update that frequently it will be a few minutes and a few miles before you get an actual altitude shown here.
3 days to a cold one!