First, females croak when they're startled or grabbed by a male when they don't want to be. Usually it's just a short chirp.

Plants needed are anything they can hide in. If you have a bioactive tank you'd use live plants (see the section on Vivariums in the forum for more info on that.) Otherwise, artificial is fine as long as there are no sharp pointy things.

Outside structures? You mean like an outdoor enclosure? Sanitizing would be a good idea to make sure there isn't chemical residue or pathogens.