Assalamu alaykum

I would be grateful if you can clarify for me the following matters with regard to salaah.

1 - in the event that I have salaahs outstanding that have not been read - do I read the fardh of those salaah before any sunnah or nafl salaahs at present - that is to say would my sunnah and nafl of the current salaah time be read or would it be preceded by the fardh of salaahs missed in the past.

2 - if for instance I read for Thohar

Four rakat Sunnat Mokadda and then need to get up and do something else away from my musallah do I read Attahiyaat.., Allahumma Salli... , Allahuma innee..., make salaam then start with the Four rakat Fard by making intention again and reading Subhanakallah again then continue as normal. Basically what is done when one needs to walk away from the mat between the sunnat and the the Fard and then walk away to do something after the fardh and come back and start sunnah again. How to end and start.

3 - if for instance I read for Thohar

Four rakat Sunnat Mokadda at the end of the 4th rakaat do I read Attahiyaat.., Allahumma Salli... , Allahuma innee..., make salaam then start with the Four rakat Fard by making intention again and reading Subhanakallah again then continue as normal. to explain myself better, what separates the sunnah and the fardh rakaats.

I hope my question is clear enough.
Jazakalaah for your answer.