Ahsanallahu ilaykum Ustadh, what is the bare minimum requirement for the final tashahud? I was under the impression it was the full first tashahud until the shahadah part "wa anna Muhammadan 'abduhu wa rasuluhu" + just "Allahumma sali 'ala Muhammad". Is this the correct understanding?

Ustadh AbdulAziz al-Haqqan

There are different sayings yes.