If its a "Tate II" then I believe yes, not sure about the Tetrasound though. I have a Tate II 101A and an S&IC(which I initially thought had the Exar chips, since they are covered and elevated but now see that there are too many pins on the detector), the Tate II needs recapping but the S&IC is still working. I wouldn't steal the chips out of my S&IC for the 101A even if they were Exar, I would sooner sell the 101A and use the money to fix the S&IC, just my opinion though.
Yes, and maybe no. The first units made used the "National" chips. According to Steve Kennedy about half of those were returned to the factory to be upgraded to the Exar chips. The later units (about half the total run) all used the Exar chips.
I have both units. The unit with the National chips seems to produce more decoding anormalities, the Exar unit is smother. In practice I rate them both as nearly equal. The S&IC has a separation control that can be backed off a bit if the decoding is producing noticeable artifacts. I seldom if ever use it with the Exar unit, usually I leave it backed off a bit on the National unit.