Go to a family law attorney and they will file with your local county court to obtain a guardianship. Usually the parent/person would have to be declared incapacitated by either private doctors or a court appointed committee. Then you will attend a "hearing" where you will speak to a judge & s/he will either grant a guardianship or not.
Yes, of course. Only if you mean the original parent's baby though.
The related link contains information which may be of help.
Yes, through the probate and family courts.
Only the courts can award guardianship.
When a person turns eighteen then technically an adult. So, no a parent can't get guardianship. Unless the person is mentally ill and can't take care of themselves. Then yes, in that case a parent can get guardianship.
The custodial parent is the parent with custody/guardianship of the child.
yes
The step-parent should petition for custody or legal guardianship.
Yes, until court ordered otherwise. see links
It depends on the State the parent and child reside in, the State the temporary legal guardianship was signed in, and weather or not a judge was involved. Usually a temporary guardianship is revocable by either of the natural parents, either by having a revocation notarized or by simply writing on their copy of the temporary guardianship form that such guardianship is being revoked with a signature and date of revocation. This is then presented to the temporary guardian and the child is turned straight over to the natural parent who now wishes guardianship returned to them. The temporary guardian can fight the issue and get the courts involved, but the vast majority of time things go the parents way in these regards. Again, it all goes back to circumstance and especially the State where this is all taking place. I would suggest googling "temporary guardianship rights", or see if you can look up the specific legal codes on guardianship in your state.
Prove the household unfit.
Single fathers have no assumed parental rights