Q 3: After Adhan (call to Prayer), some people say,
"O you the first of Creation"
although the Messenger of Allah is not the first human created by Allah (Exalted be He). Is this permissible?
It is not permissible to say any form of Dhikr (Remembrance of Allah) out loud before or after Adhan. It is obligatory to confine the Adhan to that which was legislated by Allah (Exalted be He). Whoever adds anything to it is Mubtadi` (one who introduces innovations in religion). The Prophet (peace be upon him) said:
Anyone who does an action which is not stated in this matter of ours (Islam) will have it rejected.
"Avoid novelties (in religion), for every novelty is an innovation."
What is mentioned in the question is invalid, as the Messenger of Allah (peace be upon him) is not the first human created by Allah (Exalted be He). This is false and it involves exceeding the proper limits in honoring him (peace be upon him). The Prophet (peace be upon him) said:
"Do not exaggerate in praising me as the Christians praised the son of Mary, for I am only a Slave. So, call me the Slave of Allah and His Messenger."
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.