from my experience holding my newborn niece you need to support their head and feet
when you feel like it.
of course
No because they cannot hold their head up yet
Give it about one week
Yes you can, but it depends if the mom cat trusts you enough to let you hold her babies at that young age.
No. Their mother will try to bite if you try to take them, so don't
That will most likely depend on the complications (if present) from the labor, the newborn's state of health, and the doctor's view if it is safe for the newborn as well as the mother to visit each other
I hold my rabbits at four weeks when there eyes are totaly opened and they are moving around. With my 1st time mothers I hold the mother and rub my all over her to get her scent on my hands, then i hold the babies.
"The product description explains that the baby must be able to hold his/her head upright. Obviously a newborn is not able to do this just yet. So the answer is no, the baby door bouncer is not safe for a newborn."
If the mother will allow you to yes you can, the mother probably won't be too happy but it does help to hold the babies at a young age so that they get used to people and can become good pets.
usually about the size of your hand (not including your fingers)
Depends on the queen. Mine let me touch them the second they were born. She insisted on me helping her and handleing her kittens.