You're really got a lot of good questions It's our fault that the answers're still missing in English.
So just to start:
Frame Rate Change: what's the difference in each setting?
It's a complicated question but in general options different from "to screen refresh rate" are almost meaningless if you're using GPU acceleration.
scene change - whats the difference between frame repeating vs frame blending
"scene change" is the moment between two different scenes - the image in two frame changes completely. So "frame repeating" just repeat last frame (from "scene 1") in all interpolated frames between "scene 1" and "scene 2", and "frame blending" do time-based blending between them.
whats the difference between do not recaclulate & recalculate with blocks diving
Are you familiar with mvtools/avisynth scripts? If not and you see no difference then leave it by default
For us who live in PAL countries (with 50hz TVs) is there any way to set the frame rate to 50hz?
We're all live in PAL zone but I see no problems to set my TV to something like "PC 60 Hz mode". Anyway, "to screen refresh rate" mode will interpolate frames to screen Hzs - 50, 60, 75 or 120 Hz or even more.