There are two ways to freeze the reverb. The first way is here: Freeze
In there, you simply turn the Decay knob to maximum.
In this demo, I turned the Tank Diffuse to maximum, which "retains" the sound in a several internal components of the reverb, without being diffused. What this does is that you get an almost-freezing sound which is not diffused, but rings.
To achieve infinite freezing for this second type, you have to be artful with your choice of Decay and Tank Diffuse. A good combination will yield a true freeze with this type. This demo does not do that, but you can see how it could be achieved (already the tail is pretty long).
Be aware: if you put in more sounds, it could blow up!