My sunroof seemd to work fine until I did not open/operate it for more than 2 months. I believe it is due to the cables that moves it slinding forward and backward. What I encounter was that the sunroof motor keep on rotating but it it slide the roof backward.

So here, I wonder if any of you have come across a so call manual opening lever for the sunroof and where can I purchase it.

If I remember correct its a normal hex key which you may just have in your tool box.
If the cables are worn you will have to take them out yourself and find a company that can build you new ones. You cannot buy them from Fiat they only sell the roof as a complete unit, Last time I asked they were £1800, yes thats the right price, plus fitting plus vat!
I just left mine closed.