[Feher]

There are both new (to be released yet) and older devices having styli

Stylus only devices are Boox Max, N96 ML and M92/M96. All these readers are large screen devices and you won't have to worry about pinch to zoom

With Stylus only device :-
1) Yes, There will not be any accidental taps, pinches etc
2) I do not have enough information to answer this question.
First generation of stylus that came with M92 model didn't have any buttons.
The second generation of stylus was thicker and had an extra eraser button ( i do not know if there was any other button as well).
The new models may come with 2nd or 3rd generation of stylus.
Both the first and second versions were interchangeable. So you might be able to purchase the first generation stylus and use it

3) Again the current data is insufficient to answer this question.
Onyx M92 came with 4 simple buttons + 1 Joystick button. It was possible to use the device with buttons alone and without stylus.

The new models have 4 buttons only. Without joystick button, i assume it will be necessary to use stylus for some tasks.