I am not very fond of depictions of manticores with a human head or face. Did the manticore always have a human head, or is it an influence from the sphinx, or some other monster?
The first description of the manticore with have is from Ctesias, let's read him (Translation from John Freese freely available):
The martikhora is an animal found in this country. It has a face like a man's, a skin red as cinnabar, and is as large as a lion. It has three rows of teeth, ears and light-blue eyes like those of a man; its tail is like that of a land scorpion, containing a sting more than a cubit long at the end. It has other stings on each side of its tail and one on the top of its head, like the scorpion, with which it inflicts a wound that is always fatal. If it is attacked from a distance, it sets up its tail in front and discharges its stings as if from a bow; if attacked from behind, it straightens it out and launches its stings in a direct line to the distance of a hundred feet. The wound inflicted is fatal to all animals except the elephant. The stings are about a foot long and about as thick as a small rush. The martikhora is called in Greek anthropophagos (man-eater), because, although it preys upon other animals, it kills and devours a greater number of human beings. It fights with both its claws and stings, which, according to Ctesias, grow again after they have been discharged. There is a great number of these animals in India, which are hunted and killed with spears or arrows by natives mounted on elephant
So the first description we have clearly state that they have a human head.
The text I gave as a reference is not from Ctesias but Photius. There is no book by Ctesias left, we only have citations by other authors. Photius gave a fairly solid summary of Ctesias.
A little bit of history
It is still very important to have a little view of history. Ctesias was a Greek who worked at the court of the Achaemenid emperor Artaxerxes II. The Achaemenid, you can know them as "Persians", built the first great empire and got a specific pattern: they didn't wrote, or barely. So what we know of them is mostly either by the Greeks (Herodotus, Ctesias, Arran, etc) or civilisations they conquered (Mesopotamia or Egypt) or failed to conquered (Greeks). Unsurprisingly they are rarely depicted with kindness...
And now on Ctesias, he mentioned he saw a lots of things:
- The sun is 10 times larger than in Greece
- Parrots as large as hawks with human tongue
- Rivers of honey
In "HISTOIRE DE L'EMPIRE PERSE. De Cyrus à Alexandre" Pierre Briant wrote (probably the actual reference on the Achaemenid empire) :
On est vite déçu par la lecture [de Ctésias]. L'auteur qui a vécu une quinzaine d'année à la cours d'Artaxerxes, n'en a transmis qu'une version biaisée, dominée par les tortueuses machinations de princesses perverses et les troubles complots des eunuques.
One is quickly disappointed by the reading. The author, who lived some fifteen years at the court of Artaxerxes, transmitted nothing but a biaised view, dominated by the tortuous machinations of perverse princesses and the dark conspiracies of the eunuchs.
There is English translation of that book.
I am mentioning history for one reason: understanding your source. Unfortunately the Achaemenids were no writers, we have to rely on other sources, like Ctesias, which is not reliable at all. Neither historically or mythologically.
I am not aware of any Achaemenid illustration of a manticore, neither of any story. On that regard, we barely have an idea of their religion.
Notice Wikipedia will provide you with other Greek sources but miserably fail to mention that the so called 'Persian' monster is propably not from Persian origin at all (Expect the Middle Persian words signifying man-eater). There is such scorpion creatures in mesopotamia, with a human head.
You made a bunch of fairly excellent questions. I have very few time to answer any of them. Sorry for that.