What is the minimum required in the intention for a Salah to be valid? For example in my intention do I have to specify weather I am intending Sunnah or Fard for Fajr. Do I have to specify the number of rakas I want to pray? or specify name of person who I am praying behind? etc. JazakAllahu Khairan

All of what you have mentioned are innovations, and they are haram, not allowed in Islam. Just the thought that crosses your mind that you are going to pray to Thuhr, for example, is sufficient for your niyyah (intention). Intention is not a ritual, nor is it something that you need to pronounce or say. Whether you say it in your head or out loud, all of these practices are rejected and are considered forbidden innovations within Islam.