Seems solved or i think found problem. It was/will be variant b). Pump was producing hissing sound, so decided to replace pressure accumulator, with another one. I unscrewed that one which was on car and saw ice crystal, and very thick mass almost like ice.
Also tried to connect another pump with warm hydraulic oil on my cars connector - it works quite happily, which can't be said about mine old pump. So my presumption, that liquid froze in some thin pipes. Also color of hyraulic liquid is like "beige" light brown...
Now I have to wait for + temperatures, or somehow engage Neutral gear and tow it to garage.