One nice and simple way for implementing this could be **"recently viewed questions" list,** where each item would have a **pin icon to make them stay on top**.

This should, following the android philosophy, be also remembered thoughout sessions since a "session" isn't really a concept one should have. This said, a way to **unpin all** should be provided, since while the system should not have sessions, the user might (very likely, even) still work in sessions, and thus need an option to fall back to a clean slate.