There were some hints in the anime they probably do :)
No, Mana does not kiss Atem.
It is unconfirmed by Konami or 4Kids if they were truly "in love". Although, it is known that Mana was a very close childhood friend of Pharaoh ("prince" at the time) Atem. They were often known to be mischievious in their childhood.
They never did.
This is not confirmed by Konami or 4Kids. It was only known that Mana was a close childhood friend to Atem and Mahad.
They never did.
I don't think Atem has a girlfriend because there is Anzu and Mana. He likes both girls. So, I don't think he has one.
He only sees them as friends.
No, Mana and Atem are just childhood friends. Theres nothing more nor nothing less to it.
No. They are childhood friends, it wasn't confirmed in 4kids or konami if they went out
No-one.
No one.
Atem hasn't shown any love for Anzu in the series, but, I did find a picture of their forever love. I'm a girl who is Atem crazy and I was jealous after I saw it. There's a link below of the picture.