بِسْمِ ٱللّٰهِ ٱلرَّحْمٰنِ ٱلرَّحِيمِ
السلام عليكم ورحمة الله وبركاته
As-Salaamu Alaikum wa Rahmatullahi wa Barakatuh,
We hope this message finds you in high Islamic spirits.
Regarding zanjir zani: If its performance does not harm the image of Islam and does not physically harm the individual performing it, then it is permissible.
As for the tashahhud: It is not allowed to add any sentence to it beyond what has been mentioned by the jurists.