If you are not able to finish your project on time, you need to tell your manager as soon as possible. You may not have the experience to get it done, and that is fine in my opinion, but if there are deadlines, your manager needs to know sooner than later for damage control. As you said, there are possible do-overs when in college, but you need to do what you can to make a project succeed, even if that means admitting failure - it's a life lesson, failure should be acceptable, just make sure that your own failure doesn't affect others.

You are almost at the end of your coding stint cycle - is the next six-month cycle more along your lines of what you want to do? If not, then I would look for something else. You have a goal of what you want to accomplish, and working on something that isn't even your field does not make sense for your future.

I'm not a startup founder, but I do at times question when people have tons of short stint jobs - but if it's only one, then no big deal - a history of short stints here and there can raise concern, but even then it won't be an ultimate deciding factor when I choose to hire someone.

Make sure your resume reflects your additional activities while in college - they may not be as necessary on there when you have more of a job history, but when you are first starting your resume, you want your potential employer to know what you are capable of - and this will get you callbacks where you can go in to more detail.

Good luck!