In general, I would not consider this as cheating, if its a truly competency based interview, the competencies they are looking for will not, or at any rate should not really be a secret from anyone invited to interview. Knowing the exact questions in advance would not, therefore, to my mind, give you any great advantage.
If the required competencies are not communicated, there is something interesting going on.
In your shoes, then, i would not study the material you have been sent in any great detail. I would scan it briefly and make sure that in your own preparation, you have not missed any major point. I would be putting the majority of my effort preparing for the interview in making sure i had pithy examples of my own experience ready to roll out during the interview, for each of the required competencies.
If you focus on the exact questions, you may find that you are too engaged in listening out for the exact question, when in fact the interviewer may paraphrase as they go along or use their own words to cover the different points.
If there is a major mismatch between what you expected and what they are actually looking for, this may not be the job for you. I would still go to the interview, but relax and enjoy the process of finding put about the job, the organisation and the people.