Hi! This is a homework/school assignment, right? Or why is there three versions (and the first missing) of the requirements, instead of all of these consolidated into one complete spec? Doing it in steps introduces the risk of misleading the implementation, to go down a particular path/route, which then later may turn out to be incompatible with later, previously unknown versions/requirements. What would be the benefit or reason of that, if not for teaching/exercise/testing?
Why, or what for, do you need such an interpreter for a language? What's the goal/purpose, what's wrong or missing with existing languages + their implementations? So it's probably a homework/school assignment, isn't it?
Wait, you're saying you primarily want help for it, so you do the bulk of the work yourself, not trying to plagiarize, and too you may already have some code for version 1 at least, maybe some for version 2 + 3 as well?