Did Aryans ever existed? or is this Aryan race thing a myth? People in general think that Aryans should be blonde with blue eyes, to what extent is this true? What is the Y-chromosome and mt-chromosome DNA of Aryan race?
Depends on what you want to call "Aryan race". The "Aryans" you're thinking of who are "blonde with blue eyes", is a white supremacist fantasy.
The archaic ethnolinguistic classification of "Aryans" were the native speakers of the Proto-Indo-European language, and their modern descendents. They are called the Proto-Indo-Europeans and they existed. The modern speakers of the Indo-European languages are however not one "race".
Another similarly archaic classification of "Aryans" were the Proto-Indo-Iranians peoples. This name was derived from their endonym
Arya (i.e. it was their ethnic self-designation). Their descendents are collectively known as the Indo-Iranians, which has sometimes inherited the "Aryan" designation. It includes the modern Iranians, the Indo-Aryans, and the Nuristani people.
It being tainted by Nazi/white supremacist uses notwithstanding, speaking of an "Aryan race" is still almost certainly rubbish. The modern Iranic peoples reached an Iran populated by ancient peoples such as the Mannaeans and the Elamites. When the Indo-Aryans migrated to India, they encountered native Dravidian peoples.
Their modern descendents might an Indo-Iranian language, but they are a mix of different lineages just like everyone else.