Is it true that I am completely bound by an approved preliminary building inquiry?
No. The preliminary building inquiry is made to save money. Specific questions are asked and the building documents are only developed to the extent that the authority can answer these questions. If after the environmental analysis you are not sure whether you are allowed to build a three-story house with a ridge height of 12m above street level directly on the street boundary, then you do not have to submit the finished floor plans including distance area calculations and fire protection concept. A site plan showing the location, height, and number of stories of the neighboring buildings and a corresponding building volume on the building plot is sufficient. Only the asked questions are then examined and ideally approved positively. And only for the scope of the examination is the fee charged. When the full building application is submitted later, these points will not be checked again and the fee is reduced accordingly. However, if your planning deviates from the initial draft because you only want to build two stories, it must be re-examined and full fees apply. Being too small can also be a violation of the integration requirement of §34 of the Building Code.
Most preliminary building inquiries relate only to planning law (Building Code and Land Use Ordinance), since the planner does not have to invest much energy and time in the room concept and extensive calculations only to find out later that three stories are not even approvable. In your case, however, this is not sufficient because the neighboring buildings contradict current law. Deviations from building regulations exist to your disadvantage. From the outside (forum) the situation cannot be assessed, since much now depends on the view of the caseworker at the approval authority. It is therefore all the more regrettable that no one there is willing in advance to discuss the building project with you and the planner.
Hence the already mentioned dilemma: For meaningful answers, your project must already be very concrete; the more concrete your preliminary inquiry, the lower the potential for savings but also the lower the later possibilities for variations.