Do I Need To Remember Washing Every Part Of My Body During Ghusl?
Yes. When you’re certain about these things only then you should redo it, otherwise mere doubts must be ignored, otherwise these doubts start turning into OCD in no time.
Yes, follow the same approch and maintain consistency in implementing it in every situation. In case of repeated tasks, which we are attuned to in our daily life, we are ought to do them properly even if our attention is diverted somewhere else. So unless you have a certain reason to believe that you skipped some part, you shouldn’t bother about attention deficit in such tasks.
1.b) is also pertaining to wudu by the way!
Both points are correct.