Daria: You're asking the wrong question. These sentences, however silly or senseless, are still useful in that users are presented with vocabulary items they can possibly recycle in other contexts, verb structures, word order, proper use of say direct object pronoun and past participles, etc.. My point is it's not simply about sentences we should expect to memorize for verbatim re-use; if that's what you're expecting from the site you're going about language acquisition in entirely the wrong way. It's about learning vocabulary, grammatical patterns and structures. On the other hand I guess you could memorize this very sentence for use when you find yourself in Perugia and wish to ask a local about Amanda Knox.
No, because the "l'" in "l'ha" stands for the direct object pronoun la, which refers to someone or something other than the subject. In your sentence, 'has it changed?' there's no direct object and 'cambiare' is being used intransitively, meaning that it would require 'essere' as its auxiliary not 'avere'. So: La prigione, è cambiata? I believe you could also use the reflexive form 'cambiarsi' - "La prigione, si è cambiata?" since it has the connotation of changing in the sense of transforming oneself.