Is it obligatory to wash the hands with water and soap seven times consecutively if one or more drops of urine fall on them during istinja' (ablution after defecation/urination)? And is it obligatory to complete istinja' first or wash the hands first?

If urine splashes onto the hand during ablution (istinja (definition)'), it must be washed with water until the trace of urine is removed. One wash is sufficient if it removes the impurity. There is no requirement for seven or three washes, and soap is not required until after the impurity has first been washed with water. Washing seven times is specific to the impurity of a dog's saliva. The hand can be washed either before or after completing the istinja'. The questioner, if experiencing obsessive doubts (waswas), is advised not to succumb to the devil's whisperings.