I Would like you ask what His Eminence has said regarding reciting Ali Un Wali Uallah as Third testimony? And where can one find his authentic fatwa regarding this?

Below I have written what most of the people read after daily prayers: Ashhadunna La illaha illaha, Ashhadunna Mohammaddun Rasoolillah:
Ashhadanna amirul momeenin va imamun mutaqeen, Ali un wali Allah wa Wasiurasollealli wa kahlifataho bilafazl

Is this how one should read according to His Eminence?

If the third testimony is invalid what should one read instead?

It is not part of adhan or Iqama.
This is the fatwa of His Eminence in the (Islamic Laws):
"Ruling 905. The sentence (أَشْهَدُ أَنَّ عَلِیّاً وَّلِيُّ اللهِ) (ashhadu anna ʿaliyyaw waliyyul lāh) is not a part of adhān and iqāmah, but it is good to say it after the sentence ‘ashhadu anna muḥammadar rasūlul lāh’ with the intention of attaining proximity to Allah."