Having been away from the WordPress scene since version 2.x days (I think the last time I launched a WordPress website was around 2009), I recently had reason to develop some WordPress plugins, and I wanted to ask some questions about the WordPress coding standards and API that I hope will help enlighten me (and, maybe, other PHP developers coming from other frameworks/platforms to WordPress).
Here are some questions I've had while working on my first WordPress plugin (coming purely from the development side—I'm deliberately ignoring any mention of WordPress's UI, as I don't want to inspire any trolling along the lines of 'WordPress vs. [Another CMS]'):