(format) הסתפרו doubles as the imperative. But in normal speech we do use the future tense instead of the imperative and would usually say תסתפרו.
True, there are some specific verbs in which people continue to use the more "correct" imperative form. Have you noticed how they tend to be roots in which one letter disappears? I'm not sure why that is. לכו, בואו, שבו, סעו.
can you give me a list of some other verbs that do this, in addition to בוא, לך, תן, צא, רוץ?
Actually most commands in binyan Pa'al use the imperative in common speech. The exceptions are roots which פs are נ or ר, and maybe some other specific roots that I cannot remember right now.
The initial נs and הs as well as the middle יs and וs usually disappear in certain verb forms
I am not a native speaker, but I would say "Get a cut before Wednesday". Is it wrong?