Offset Tracking Tutorial - bad work

Not clearly: In step 4 “Apply Orbit File operator” is applied to two files (master and slave images)? Or only to one - master image?
Not clearly: in step 5 (DEM Assisted Coregistration) are used both files, made with “Apply Orbit File operator”- master and slave images with (… _ orb)? In Offset Tracking Tutorial on “Figure 13 Coregistered Stack Product”, the name “Stack - file” has no part “_ orb” as it is visible on “Figure 10 Select master and slave products”, that is on step 5, images improved with “Apply Orbit File operator” with (… _ orb)is not used?

Only one example, not clearly what limit of the minimum speed of the movement of glacier for this method with images Sentinel 1?