i have a one year old yellow passionfruit vine, it has lots of flowers ( i live in Sydney, Australia);
but these flowers do not form fruit, i even hand pollinated some flowers.
is it because passionfruit does not form fruits in the first year ? or is it lack of certain trace element ?

A lot of Passiflora are not self fertile. Yours may be one of them. I have had success with using a technique that involves microwaving pollen in order to circumvent the sterility problem on some plants. I haven't tried it on Passiflora yet. Give it a try and please report back with any success or failures .. I am wanting to start a list of plants this technique works on. So far I've had success with Hibiscus moscheutos 'Midnight Marvel' and Albuca spiralis.

Here is a link that explains how to do it:

The thread "Microwaving Pollen & Seeds from Midnight Marvel!" in Hibiscus forum

Some of my passion vines don't make fruit right away, as well. The first year I often only get one or two fruits. Second year, it picks up and by the third year it's in full production. Then the vine dies after maybe the 4th year every time. Trunk rot.

Take cuttings and start a new vine in the 3rd year if you want to keep it going.

Can you take pollen from a different passionfruit vine, refrigerate it, and then hand pollinate this one at a later date?

I do believe that your problem is probably due to them being a tropical plant. They need tropical conditions to fruit.