To ensure that all wires are tested?"The above understanding is from the OSG @scousespark"
It's clear to me that you don't understand what the reasons for doing the tests are and what the results tell you, you only understand that certain tests need to be done. You need to understand WHY these tests are needed and what the results show. If you had a basic understanding of how electric circuits work, say GCSE physics level, you would be able to deduce the answers to very many of your questions yourself. This would also aid you immensely in understanding what testing is all about and why it is done in a certain way.
On a simple one-way lighting circuit with a single switch, why do you think it is necessary to to the insulation test with the switch in both positions?
I was unclear on when you have multiple switches and hence multiple switch positions to test.