With regard to your first question, you are probably at one of the best places on the web to learn. This site is administrated, moderated and regularly visited by a large amount of competent and certified Electronic Engineers, along with numerous hobbiests with a good amount of knowledge.
You have already identified that there are hazards to be wary about when experimenting with higher voltages and/or current, along with presenting a cautious approach, so that's a plus.
If you have an idea or query for a potential circuit or particular application, by all means post the relevant outline and schematics, then wait for a review. You may receive a little critique...perhaps positive, perhaps negative, but the content which you actually put forth for discussion will likely determine the quality of the replies.
Regards.