Speed Restrictions
As I recall, the 250 knot restriction was introduced in the late 1960s. The 210 and 180 restrictions came a few years later, after discussions between the FAA and airlines.
I do not think there is any airspeed tolerance to speed restrictions given by Approach Control. Using the standard 3 mile in trail spacing, if the lead aircraft reduces to 170 knots and the following aircraft increases to 190 knots knots, there will be a loss of separation. I have been given a side step to another runway by Approach Control, and another time a go-around, because the preceding aircraft did not comply with the issued speed restriction.
You can be stable by 1000 ft. in a B747-400, if you establish gear down, flaps 20, and 180 knots until 5 miles. Critics will say you are using flaps for drag, but it is better than using flaps 5 until 5 miles, thereby risking an unstable approach.