Would like to ask regarding including the wilayah of Ameeral Mu'mineen in salah in the tashahhud as i have seen a video of this. What is your opinion or advise upon this? Are we allowed to include before salaam?

Below is the answer from Ayatullah Ul udhma sistani:

In the Name of Allah, the Beneficent, the Merciful

"Ashhadhu anna aliyan waliyullah" is not part of the tashahud therefore; you must not say it in your prayer. It is recommended although to recite it in the "Athan" and the "Iqamah".