Doing older reviews

First off, you should know asking this likely is going to spawn a debate over whether or not you should be reviewing kanji/vocab that you haven’t burned, and if that messes up the SRS factor. However, barring that, if you feel like reviewing, if it’s not burnt, I’d suggest either going through the lesson page and just manually trying to read them, or getting Anki/any program that has flashcards and just inputting what you want. Someone else can suggest decks, I’m not big on Anki.
However, if you want to review stuff that you’ve burned, I’d suggest downloading this burn review script if you know how to use userscripts.