ISP Decimator G string [traced]

[POTL]

This is vero schematic
I have 2 questions
1) DA 1.1 Whether it is an obligatory part of the circuit or just closes the second half of the chip
2) DA 2.2 The voltage divider is perfectly capable of operating without a chip, why is it here?
P.S.
JFET КП303А, D7,C12,R34,R42,LED,D11 Must be removed if you want true bypass.

[alexradium]

these are normal textbook practices,just read one and you get it.

[bmxguitarsbmx]

You could probably get away without the DA 1.1 buffer.

I wouldn't advise simply using a resistive voltage divider + capacitor to establish a bias voltage for this circuit as the circuitry draws current asymmetrically from the supply. This asymmetrical current draw will work against the long time constant of the bias supply to cause bias voltage shifts that may cause clipping and unpredictable results. The often seen resistive voltage divider + cap bias supply is really only a low impedance to A.C. signals. Any D.C. offset, transient signal, or even circuitry with asymmetrical clipping/distortion can cause problems with the very common voltage divider + cap buffer.

Hope that is helpful/ makes sense.

[POTL]

Already with all understood.
Now I'm confronted with another question, can I replace LF353 with TL072 or TL082.
Or is the circuit designed for LF353?