Taking on a project beyond their skills? Nobody I know would ever do that! ;D I guess that depends on what you mean by that. If it is a case of doing something his has not done before(ie an sql database) versus Quantum theory.....

All the people I know will attempt stuff they think they can overcome. Don't we all?

As to your questions. I never push advice because a person can resent you if it fails and even if suceeds. I tend to offer opinions on what could happen, approaches, etc.

As to the Personal Learning project. Heck I would help out. Might learn something new. Usually, a person will view this as a hobby like quest and don't get too frustrated by it.

Homework project? I tutor math so if I knew what he was working on I would "guide" him towards answers. Just fixing it does not teach him anything.

Community Service. Shoot if I have the time I would help out. People "usualy" don't care who does the work and are pretty happy to see anybody help out.

Work project? Done well? That is open to interpretation. But if it had the capability of blowing up my stuff. I would help out. I don't care about the recognition as I tend to give everybody a chance. But if they clearly take advantage of me then the next time I view them as "fool me once shame on me, fool me twice...."

The Reactor program. Welll sounds interesting but if you work there you are supposed to be capable of doing the work. Besides there are so many checks and balances that you have to do. I would not be worried. Well there are a couple people I might be! :P