Ok. I know Audi's need a special brew for EVERYTHING. PS fluid no exception.
But even under the special brews (Pentosin), there is:
CHF7.1
CHF11S
CHF202

Back of the label says: 202 mixes with 11S, but DO NOT MIX with 7.1

a) What is the RIGHT one for my 1998 A4 B5 1.8T quattro manual (with KYB or so PS pump, NOT ZF)

b) What are the differences between the 3 fluids? I assume they are all MINERAL fluids. Some synthetic, some non-synthetic?

c) What is the difference to 'normal' PS fluid (some even use trans fluid as PS fluid with success)?

d) When low, I filled up with 11S (got it at NAPA). Bad idea?

e) Once I know what SHOULD go in, I want to drain the entire PS system. last car I did that (Allroad with 2.7T auto), removed the return hose to the reservoir, ran the engine and worked the steering wheel back and forth until nothing came out. What is the CORRECT procedure?

f) While we are at it: where I can find out what PS fluid other VW/Audi need (I have a bunch of them in my fleet: 96 A4 2.8 auto, 98 A4 1.8T manual, 99 Passat 1.8T manual, 02 Allroad 2.7T manual, 02 Allroad 2.7T auto.

 

CHF7.1 is for older Audis , like 80's up to early 90's. Then they went to the CHF11s. The CHF202 is used in Porsche & Volvos.
I do not know the difference , do know they are mineral oil based.