My only word of warning (based on my experience with interviewing people who then turn down the job) is that if you do get offered a position, and refuse it, it could affect your chances of getting employment with that company in the future. It's only a small consideration, but if you are applying to companies for practice, but you would genuinely want to work for them if this other offer hadn't occured, it might not be a good idea to give them the impression you are a 'timewaster' (which is invariably the label interviewers give to candidates who do this very thing). It could come back and bite you in the future.
Just a thought.
Just a thought.