Athaan أذان and Iqama are recommended and we say Ashhadu Anna Aliyyan Waliyyullah being the main fact of proper faith after Tawheed and Nubowwah. This was been announced in Athaan immediately after Ghadeer Khum decleratiin.

Tashahhud is not recommended but obligatory. In Tashahhud we are bound to say exactly what was been said by the Prophet (SAWA) and Ahlul Bayt (AS). All  authentic Hadeeths from Prophet and Ahlul Bayt teaching us Tashahhud have the same Tashahhud with out adding any sentence on it. Mentioning Ameerul Mo;mineen (AS) in Tashahhud is allowed or recommended as part of supplication like (ALLAHUMMA SALLI Ala Aliyyin AMEERIL Mo;mineen) and not as a part of Tashahhud. Du’a is permissible in every part in Salah, but Tashahhud must be recited as it was recited by the Prophet. and Ahlul Bayt (AS).

Wassalam.