All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
What you have mentioned that in Tashahhud a praying person extends his index finger when saying “Laa Ilaaha” and retracts it when saying: “Illallaah”, is a statement of some Hanafi jurists. For instance Ibn Al-Humaam said: 'According to Al-Halawaani one should extend his index finger when saying “laa ilaaha” and retracts it when saying: “Illallaah; i.e. he extends it in order to deny [associating others with Allaah] and retracts it in order to attest that None has the right to be worshipped but Allaah.”
Nonetheless, we do not know any evidence proving these details in the Sunnah of the Prophet .
Allaah Knows best.