"But I noticed that the female mosaic tried to ride on top of male" This is not a gender specific thing or even a breeding specific thing. Yes males can/do mount females, but younger gliders male or female will ride on older gliders backs as they do on their parents until they are mature.
So if your female is a bit younger than the male or if the male is a bit bigger than the female she may ride on his back indicating she's still got the baby mode going on.
I've had a 3 yr old female ride on her cage mates backs because she was considerably smaller than the other 2 were and the other two were not bothered by it all. The cage mates were a female of the same age and an older neutered male.
"and she rubbed her head on male neck, which these behaviour are always done by a male supposingly."
This is a video of the 3 yr old female that rode on backs mentioned above rubbing her head on the neutered males neck after they were introduced.
she's not rubbing HER scent on him, she is rubbing HIS scent onto herself. males have 3 scent glands, 1 on their head, 1 on their chest just below their neck, and 1 anal gland. Females have 2 scent glands, 1 at their pouch and 1 anal gland.
This is normal behavior for females that are introduced to a male (neutered or intact) that's not to say all females do it....but it's not abnormal if they do.
Right where she is licking you can see his scent gland, which is right where she was rubbing her head