About Demonology : I don't really know, it's one of CHile's mechanics, so it's obfuscated to us. Maybe this guide created by an user might help.
https://www.princesofdarknessmod.com/wiki/index.php/Apprentice's_Guide_to_Demonology
About Necromancy : They probably are missing the corresponding flag, thanks for the report.
About the Banu Haqim : It's complicated. Assamites lore has evolveda lot with time. I will try to give a summary.
Haqim was, overall, a nice enough guy. A judge and an hunter in Enoch, he was a third generation not really involved in the others' shenanigans and served as a respected mediator. He didn't participate in the revolt and was, for all intents and purposes, spared by Caine. His "curse" to have his skin darken with age is laughably lenient compared to something like Nosferatu's one.
Haqim continues on, founding Alamut and forging his clan into anti infernalists first and foremost. With the Salubri, he is at the forefront of the Baali wars, being a central force there (with some... dubious decisions, like embracing Ur Shulgi, but still coming from a "good place").
During one of those Baali Wars, the Baali capture Izhim ur Azrael and uses him to curse the Warrior Caste with a thirst for diablerie. The second Banu Haqim curse is born, but is still fleeting at the start, easily controlled.
Haqim disappears from Alamut after a civil war nearly explodes during the Sparta/Athens war. He comes back to visit from time to time, until he doesn't at roughly the start of the common era.
The Baali Curse starts to get stronger. The Warrior Caste creates a proto "Road of Blood" to not get crazy as they have to contend with it but still not succumb to frenzy and such.
Comes 1242. Enkara (Izhim's childe) tries to save her sire (an event in the mod) but actually unleashes him (he was corrupted) and the full power of the curse on her clan. Everyone is now cursed with the Baali Curse and the Road of Blood becomes a matter of survival, adopted by the vast majority of the clan.
That's the most accepted story of the Banu Haqim, from books like Libellus Sanguinus, Clanbook Revised or Cainite Conspiracies.
But before those books, it was completely different. These earlier accounts were later said to be a distorted version of the truth told by the followers of Ur Shulgi, the Web of Knives (represented by path of righteouness in the mod).
In these earlier accounts, Haqim embraced himself, was a righteous hero and everyone else is unworthy of even sharing the divine blood that Haqim used. So it must be reclaimed, everyone must be diablerized and only the worthy Banu Haqim must survive at the end.
Basically, they are crazy blood addicted fanatics followers of a very powerful Methuselah (Ur Shulgi). Their account of Haqim's history is contradicted by basically everyone else, and is wildly accepted as nonsense. But they obviously believe in it fanatically.
Using the reinforced Baali Curse as a proxy (the need for diablerie is easier to accept when you think you are mandated by a righteous blood god to do it), the Web of Knives gets stronger and stronger in Banu Haqim politics. The Assamite leadership then "accepts" the Tremere Curse (the third and final curse on their clan) to try to stem this tide, since the Tremere Curse makes them unable to diablerize.
Then Ur Shulgi wakes up in modern, casually breaks the Tremere Curse and takes control of Alamut. A schism is born between followers of his (blood addicted fanatics) and followers of Al Ashrad ("traditionalists" Banu Haqim that ends up in the Camarilla).