[Oldcodger]

I'll answer #1 with another question. When did the operator direct routes come into existence? Before STD became fully into effect there was a set of routes for direct dialing solely for the use of operators with a set of differing codes. I first heard of it when some engineers at Stone ( Yarmfield college as it's known these days AFAIK) used this to phone home for free and were caught.
From memory of the heady days in a TRS, I seem to remember that there were set levels depending on the grade of the junction. I seem to remember that the worst case was -4dB overall loss( sent at 0dBm and received at other end receiver at -4dBm , approx half power/or voltage if you prefer)