Responsive update checker: not quite clear on this; we already pop up update prompts in the non-Play version, we just only check once a week because we assume a large % of people running that version are on terrible or expensive internet connections. Do you basically just want the update status to be always available in a settings screen somewhere?
Song/Kai toggle: this is actually a bit awkward to make into a setting because some characters are only available in one style or the other. Basically we remember whatever the last thing you manually toggled to is and default to that (as we do in a couple of other places with similar partial-availability problems, like the popup definition bubble dictionary selector) - translating that to a setting feels like it'd just sow confusion.
Load time check: we're pretty confident that can't be improved by settings. Pretty much anything at a level that can be done optionally in settings can also be deferred until after the app has loaded; most of our app's actual load time is taking place before our code even runs, the reason it's gotten slightly worse in the last few years is because our app keeps getting bigger as we add new features and so there's ever more stuff that Android needs to load into memory on startup.
Our load time has actually grown considerably more slowly than average mobile device CPU performance, so we expect most users haven't noticed (any slight slowdown was more than canceled out by their last hardware upgrade), but if your device is old enough to run a 4-year-old version of Android then about the only load time solution I can suggest is that you switch to our old version 2 (
http://pleco.com/getoldandroid) which is a lot smaller + hence should load a lot faster.
We do automatically prompt you to back up flashcards once a week by default; you could probably also configure a third-party backup utility to back them up manually. You don't need to export the cards to back them up, a 'backup database' should be enough - we're working on a consolidated backup system for 4.0 (everything would end up in a single database file, even settings).
If you turn on "Use builtin input method" in New Test / Test Settings, that should let you use SwiftKey.