Offering Janazah Prayer in a graveyard

Q 1: What is the ruling on offering Janazah (Funeral) Prayer in a graveyard? If your reply is that this is not permissible, then how do we reconcile this with the Hadith of the Prophet (peace be upon him) wherein he offered Janazah Prayer in the graveyard over the woman who used to clean the Masjid (mosque)?

A: Anyone who misses offering the Janazah Prayer over a deceased, it is Mustahab (desirable) to offer it over their grave (Part No. 7; Page No. 257) within the period of a month from the day of burial. The grave should be in a middle position between the praying person and the Qiblah (Ka`bah-direction faced in Prayer). It is narrated in a Sahih (authentic) Hadith on the authority of Abu Hurayrah (may Allah be pleased with him): There was a black woman (or a man) who used to clean the Masjid (mosque). The Messenger of Allah (peace be upon him) once noticed that she was absent and asked about her, but he (peace be upon him) was told that she had died. He (peace be upon him) said, 'Why did you not inform me?' They responded in a way which conveyed that she was of little importance. The Prophet (peace be upon him) said, 'Lead me to her grave.' They led him to it and he prayed over her. He (peace be upon him) said, 'These graves are full of darkness upon their occupants and Allah (Glorified and Exalted be He) illuminates them by virtue of my prayer over them.' Imam Ahmad said: "Who can doubt the validity of offering Janazah Prayer over a grave? The act is reported to be done by the Prophet (peace be upon him) through six lines of transmission all of which are Hasan (Hadith whose chain of narration contains a narrator with weak exactitude, but is free from eccentricity or blemish)."The Hadiths stating that the Prophet (peace be upon him) offered Janazah Prayer over the grave of the deceased after burial are classified as Sahih and Mutawatir (a Hadith reported by a significant number of narrators throughout the chain of narration, whose agreement upon a lie is impossible). It was narrated by Ibn `Abbas, Abu Hurayrah, Anas ibn Malik, Yazid ibn Thabit, the brother of Zayd ibn Thabit, `Amir ibn Rabi`ah, Jabir ibn `Abdullah, Buraydah ibn Al-Hasib, Abu Sa`id Al-Khudry, and Abu Umamah ibn Sahl (may Allah be pleased with them)May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.