can i only get three partner?
if more than three, how to get them?
how to get all armors?

You can only get three partners at most. For the rest three, you can never have them.
But by using their deck, you can fill up the card collection slots of those three partners and their armor-digivolve forms.
Originally you can refer to our walkthroughs above to get the armors, but unfortunatelly and apparently you';re not allowed to talk here anymore.