Where do I focus ? On the outer nose or outer nose with upper lip? My question is that where do I focus ? The outer nose or outer nose with upper lip
The instruction is: sati-parimukkham, or parimukkham-sati.
This means: mind-around-mouth
It also means: mind-around-face
It also means: mind around the front
It also means: mind around the interface [between the personal and the external]
It also has been interpreted as meaning: mind the business at which you are about (that is minding).

This instruction is found in cases where a formula for meditation is being set forth, not exclusive to minding the in and out breaths.

There is no instruction that reads: 'focus where the breath is felt' or 'at the nose' or at any specific place. Try to focus on the point where the breath passes the nostrils you will quickly see that you cannot find that place. It moves around at light-speed!

That is why the instruction reads "around" (pari). The point is the focus, not the locus. This is also important as a preventive measure: our job here is not to maintain a state of concentration on any object. We are trying to develop concentration (or better, focus) as a skill with a tool to be used in understanding other things. You are not going to Nibbana with your mind focused on your nose!

Follow the instructions without trying to pick it apart and you will see the advantages of minding around the mouth as a starting point, minding the face as a matter of minding the sense-reactions, minding the front as minding the whole body, minding the interface as minding the inter-relations of the body and the external world, and minding your business as keeping you focused on the task. Round and round, up and down, back and forth. A spectrum.