There is no basis for shaking hands or saying “Taqabbal Allah” after finishing the prayer; that was not narrated from the Prophet (peace and blessings be upon him) or from his Companions.

Having the custom of not eating meat during al-Muharram comes under the heading of innovation that is not permissible as a means of drawing closer to Allah.

-The Prophet recommended saying “Subhan Al-Malik Al-Quddus” three times after Witr, raising the voice on the third time. -There is no evidence for reciting this Dhikr between the Rak`ahs of Tarawih. -Adhering to the Sunnah in worship is obligatory, and collective recitation of Dhikr—when unsupported by authentic evidence—must be avoided

Reciting Al-Fatihah at the time of the marriage contract or engagement has nothing to do with the Sunnah; rather it is an innovation (Bid`ah).