I made some connectors, when i tried to place those on the board it takes pin1 as a pick and place is there any way to change the pick and place to center.
also if i want to change a via(no net) property to some other kind how could i do it without effecting the others vias of same kind
The pick and place data is based on the symbol origin. To change this you will need to open the library symbol, and move the part so that the origin, (0,0), is where you want it. In this case you will want to move the center of your connector to 0,0.
You may change your symbol origin to the geometric centroid of the part to achieve what you are asking. Keep in mind also, once you place your component that you have some flexibility in moving the part in Allegro. There are several options for selecting the origin in the control panel; Symbol Origin, Body Center, User Pick and Symbl Pin# (use any pin as the origin).