Good questions
But... not much has changed with side-loading. If your device supports it, and most Android devices do, what you suggest should be a piece of cake to achieve, and the general instructions in the article above should support you in doing that. In your case, you could easily install a program, back it up to .apk using Astro, then use Astro to copy the .apk from the backup folder on your internal memory to the external SD. Uninstall the app, and then later, when you need it, you'll just browse to the external SD using Astro, double-click the backed-up .apk, and it will re-install (this will also give you a portable library of .apk files from the Google Play store even when you don't have an internet connection). When I talk about examples of how Android users are more empowered than iOS users, this is one great example of that in action.
