I can answer a few of those:
The first displays evidence of manufacturing -- for one thing, the skull's sutures (cracks) are missing (they should be there) and features that must
be present (holes below the eye sockets where the nerves run, etc) are "mysteriously missing" from the skull.
Then there's this quote:
During an archaeological dig in Sayre, Bradford County, Pennsylvania in the 1880s, a number of human skulls were unearthed. These skeletons were
anatomically correct, except for the anomaly of their projections, two inches above the eyebrow, and the fact that their average height in life would
have been around seven feet tall. The bones were sent to the American Investigating Museum in Philadelphia, where they were stolen - never to be seen
No such thing as "The American Investigating Museum". And "we found this and took a picture but it Mysteriously Vanished or was stolen" is a
hallmark of a hoax tale. They don't want you finding the clay covered object because anone with half an ounce of curiosity would say "this thing is
covered with clay. Clean it up and let's look again."
Horned people (keratinism) is a known genetic anomaly. I have seen one form of it caused by a virus similar to the one that causes warts.
Starchild skull was tested at one time and found to be 100% human, though the person who has charge of the skull didn't like the verdict
(apparently). Hydrocephalus has been the suggested diagnosis.
Peruvian skulls -- they're showing you one of many hundreds that they have. They know that this is caused by binding the heads of the babies. These
are fully human and other than the binding causing the head to have a strange shape, there was nothing wrong with the people. Humans have practiced
binding of other body parts, and even in adult life the skeleton can be reshaped to some degree. The Padaung tribe is a good example of bone
reshaping of the neck region:
Ahkenaten: they show you a stylized Egyptian picture and present it as literal truth. Their mummies are around and while they do have long heads,
their heads fall within the range of normal human beings (look for the x-rays and you'll see. National Geographic did a presentation on this).
Small skull: that of a child about 3 years old (judging from the teeth) who died from hydrocephalus. The fontanelle ("soft spot" on the top of a
baby's head) has not filled in yet and the sutures (cracks) are very prominent. The teeth and jaw show that this is a child's skull.
Half skull: hydrocephalus again, but a more slowly progressing case. This person reached adulthood, but just barely.
"Bulgarian skull"... is not a skull, nor is it of human origin. It does appear (a Hans pointed out) to be the sacral area, but it's not human... I
believe it's bovine based on the size and the "T" shape of the top area. Notice that they never show you the whole thing -- only the angle that
can be "called" a "skull." You can see the sawed area where the sacral spines have been removed to make it look more like a skull. You can see
the dip of the hip sockets, too.
There are no other views of it as far as I know... only the "face forward" view.
I predict that this is another "mysterious skull" that "vanished mysteriously" after being found (and that if you pressed the people who found it,
they would say they sent it off to some scientist somewhere who never received it.)