Eigen Mode Solver or Transient Solver in CST?

All Dears,

1-For Analysing 2D Photonic Crystals and obtaining their characteristics such as Transmission Spectra and Photonic Band Gap(PBG), we should use Eigen Model Solver or Transient Solver (in CST software)?

2-what parameters should be noticed in simulation(I mean Boundary Cond.,Freq.,Ports,Excitation Signal,...)?

3-Is CST 5.1 caplable of doing that or I should use 6th edition?

I've a project which I can upload it upon request.

Regards