As I uderstand for workflow with gamma 2.2
RGB 255.255.255 level 1.0 = RGB 255.255.255 level 1.0
RGB 128.128.128 level 1.0 = RGB 255.255.255 level 0.5
RGB 64.64.64 level 1.0 = RGB 255.255.255 level 0.25
Is it true? Here my logic stopped.
Level is just a number the result from color picker gets multiplier with. So your equations will hold with any gamma.
If I need to mix color with bitmap for reflection 1:1 what will be correct for corona's algorythm? To use amount 0.5 for map and color let's say RGB 64.64.64 level=1.0?
Is it same for using map with amount 0.25 and pure white with level=0.25?
If you need to mix something, you can use CoronaMixTex, or just set the two values (color and texture), and set texture amount to 0.5. Level is applied AFTER the mix. Or it is applied before, but to both the color and the texture, these two formulations are equal.
As for the gamma workflow, corona will always do calculations in the linear space, so you can just use "what looks good" method ;). Of course, what will look good are input textures with removed gamma, which does 3dsmax for you automatically if you set gamma correctly in preferences.
And another question:
As I understand, if I need some specific color, I can't just type it's RGB in diffuse color slot, because my gamma 2.2 will change it. Do CoronaSolidTex will work correct in this case?
AFAIK the gamma correction is NOT applied to the numbers you type in, it only affects how the color is displayed. So typing 127 in will always give you 50% white.