If you have a future event and the time is indicated by "when ____", then you use present simple. We know it's a future time because of the main clause. eg. When I get home, I'll call you. Search for "time clauses", and you'll get more detailed explanations. I hope I understood your question correctly.

To me - even that is not always the case. I'll leave this for a teacher to answer.

In "conditionals" e.g. we say: "If I were you I would do this..." The time of the two parts will change to future or past. I'm asking if there is such a rule for this one.

sorry - I don't understand your question. Please remember that many of us that try to answer questions are native speakers, so unless we are teachers, we may not know any of these 'rules' that you do. It would help to explain this rule, and give some examples.