I agree on the advice on applying for jobs you don't want first. If you're like a lot of people, you're nervous during interviews and practice makes perfect. Maybe you'll encounter questions you didn't expect or have a great answer for. Maybe you find out that people really do quiz you on all the textbook CS stuff you learned in college and subsequently forgot.
If you get a job offer out of it, that will build confidence for when you apply for the job you want.
Please only do this if you're fresh out of college (or otherwise new to interviewing for tech jobs). Interviewing candidates is hard enough on companies without spending time on people who don't even want the job.
I don't know. Often I'm not sure if I want the job or not whem I apply, so I see interviews as an opportunity to learn more about the company. Many companies are very different in what they ask for in a listing and what they're actually like. It goes both ways.
I understand your concern, but I agree with the advice whether just out of college or not. Interviewing is a skill just like any other, and if it has been more than a year since the last one, chances are you'll be rusty.
If a candidate is in the interview, there must be a modicum of interest, and is a great chance for the employer to sell it's position. And of course, as an interviewee, it is mutually beneficial to avoid wasting both parties time by expressing disinterest as soon as possible.
If you get a job offer out of it, that will build confidence for when you apply for the job you want.