The Fardh - obligatory rakats of Asr is 4 and a total of 8 rakats: 4 sunnat, 4 fard
The Asr prayer is one of the five mandatory salah (Islamic prayer). The four rakat Sunnat followed by and four rakat Fard .
The first four rakat is sunnah, so some people do not pray it and begin with the 4 fard.
Fardh - obligatory someone who ignores Fardh intentionally, knowing that it is an obligation, becomes a kaafir (disbeliever) (that is the opinion of most scholars)
Sunnat - those actions of Hazrat Muhammad (ﺻﻠﯽ الله ﺗﻌﺎﻟﯽٰ ﻋﻠﯿﮧ ﻭﺍٓﻟﮧ ﻭﺳﻠﻢ) (peace be upon him) that were done.
Time: The time for Asr prayer starts when the shadow of an object is the same length as the object itself and end when sunset.
There is a hadith which says; “Whoever completes Fajr and Asr prayer will enter Jannah.”
And Allah knows best