Is it obligatory to enter into a state of Ihram for visiting Medina for those coming from Mecca or Abha, and what is the procedure for that?

Entering Madinah does not require a special ihram; a visitor enters in their ordinary attire. The visitor must be mindful of its virtue and status as the Sanctuary of the Prophet, peace and blessings be upon him, and show proper reverence by refraining from committing sins. They should frequently visit the Prophet's Mosque and pray therein (prayer there is equivalent to a thousand prayers), visit the grave of the Prophet, peace and blessings be upon him, and his two companions, visit the people of Al-Baqi', and visit Quba Mosque and pray therein (prayer there is like an 'Umrah). They must adhere to obedience, remembrance of Allah, and diligence in worship throughout their stay.