What is the ruling on someone who entered Mecca for a visit and 'Umrah without ihram, then entered ihram after three days, and what is the necessary duration for the 'Umrah to be valid?

If one intends to perform Hajj or Umrah from outside the Miqats, it is obligatory for them to enter into Ihram from the Miqat. If they fail to do so, they must either return to the Miqat or offer a sacrifice (fidyah). For one who is within the Miqats and intends Hajj or Umrah, it is obligatory to enter into Ihram from their location, unless they are within the Haram boundaries. In the latter case, they enter into Ihram for Hajj from there, and for Umrah, they must go outside the Haram to the 'حل' (such as Tan'eem) to enter into Ihram from there. This is supported by the hadith of the Miqats narrated by Ibn Abbas, and by the action of Aisha (may Allah be pleased with her) during the Farewell Hajj, when she went out to Tan'eem for Umrah. If someone enters Makkah intending Umrah, it is obligatory for them to return to their Miqat, otherwise, they must offer a sacrifice, and this obligation does not fall away with the passage of time. If one did not intend Umrah before entering Makkah, they enter into Ihram from where they make their intention, and if they are within the Haram, they must go out to the 'حل'.