Is the Hijr of Isma'il (peace be upon him) truly a grave for him, and who narrated that, and what is the real story of the Hijr, and why does the circumambulation take place from outside it?

Abd al-Razzaq mentioned in al-Musannaf the existence of the grave of Isma'il (peace be upon him) in the Hijr, attributing this to Ka'b al-Ahbar. It has also been narrated as a marfu' hadith with a weak chain of transmission. The reason for the obligation of circumambulating (tawaf) from outside the Hijr is that the Hijr was originally part of the House (Kaaba), but Quraysh was unable to complete its construction.