You would definitely want t bring it inside,,.... And instead of letting it grow on the walls.... Put a stick behind it and it will attach to the stick....
that would depend on the plant. The more love it gets the fast it will grow. When it has grown long enough for you.... You just cut it and plant your cuttings. I have mine out side. I let it grow(mine was almost 8 ft tall) However, I bring all my plants into the garage because I live close to the water and the frost may harm it. I have never let it out in the freezing temps. so I really don't know how cold hardy it is. but if you google ricrac cactus youll learn then you need to know. lol...