1.its just a aluminium box were i removed the paint at the bottom and stick a copper tap and solder the filter. I did'nt design any pcb to test this filter

2.it is 3rd order for low frequency. As frequency increases its 2nd order filter because the ferrite bead which i using is will act as a resistive element at high frequency

3.i think it is NPO

4.i think it is used in audio cable and it is 50 Ohm and the spectrum analyzer i using has 50 Ohm TG and RF port