Does all the citrus fruit contain Citric acid and Ascorbic acid?
Whatever the colloquial/vernacular/etymological meaning of "citrus"; when it comes about scientific names; Citrus is a particular genus. It do have many species. 


  "Amla being a citrus fruit" 


No. Amla (Phyllanthus emblica) is not a member of genus Citrus; not even allied. 

Ascorbic acid is just another name for Vitamin C. It is also present in common edible citrus fruits.