I want to get a clear understanding with the ability Frisk and Synchronise

 

Are they work in server?

If do, do Frisk work if I am not use it as the first one pokemon when I meet wild pokemon?

Synchronise works with 50% to make the encountered pokemon have the same nature as your pokemon with synchronise.

Frisk find the item on the encountered pokemon if the said pokemon has an item. It will appear in your battle GUI "I.E. Wild <pokemon> appeared, <pokemon>'s frisk has found x item on <Pokemon>

Note : Synchro will not work if your first pokemon has synchro but fainted, needs to be pokemon who sees the wild encounter.

Hope that clears it up.

How about my first pkm is synchronise ability, and then I switch Frisk pkm to check the wild pkm items? Is that work if I use like this?

Yes, it will work like that.