That doesn’t sound good
I don’t want to unsettle you, but only raise awareness of possible problems, especially since you initially asked quite generally what needs to be considered. I have not dealt with the city council resolutions. I also do not know the history of the development plan or the local entanglements. There are certainly capable and practical city council members and also responsible authorities, so I may suspect difficulties that do not actually exist.
If the municipal representatives have decided to develop a building area, it is common practice (and legally required) to hear and involve the citizens, especially the affected owners, before the preparation of a development plan. Then the concrete planning takes place. Then the development plan gains legal force. If several owners are involved, a land readjustment procedure according to the Building Code is initiated, the areas are newly arranged, allocated, developed, and marketed.
Here, obviously, the readjustment was waived, then a dispute arose between the city and at least one owner, and the procedure stalled – city council, citizens, owners – everywhere offended parties blocking each other and no longer communicating, not even through lawyers. Nevertheless, to create building land, which is obviously in the interest of another owner, a makeshift solution involving as few parties as possible is now being used through private development. IMO, however, the development plan should be amended. If the farmer goes bankrupt, or not always so pessimistically, falls in love and moves to Mallorca head over heels, you end up with a plot without development. I think it is important to find out what securities are included in the urban development contract. What is to be done with the designated traffic area? Should it be transferred to the city upon completion? What should be done with the "auxiliary development," which is not designated as a traffic area? How are development costs allocated? Who has to maintain these areas? Is there a binding timeframe for the completion of the development?
But that wouldn’t actually be feasible either, because the dead-end road (and the rest of "our" plot) lies on a foreign plot, owned by someone else (and that was already the case back then).
The same applies here: these contradictions would not have arisen with a proper readjustment procedure. If the development plan cannot be implemented for whatever reason, then it must be amended (fully redesigned here). They don’t want to take that trouble, and that gives me a bad feeling – perhaps unjustified.
Yes and no, the concept drawing was approved as an attachment to the meeting of the local council, the committee for urban development, and the city council.
As I said, I don’t know the professional competencies of those involved. I see the scope for interpretation regarding the transfer of the development plan to the current land registry as exceeded here. But if the geodata professionals on site agree, my view is irrelevant.
the other owner
How old?
I think the reason the dead-end road is missing is simply that it would lie on a "foreign" plot that has nothing to do with the current development.
A skilled drafter would then let the depiction of the applicable planning law end at the planning boundary, just as he did with the rear building boundary on "your" plot. Here, however, the building boundaries have been continued, and the depiction of "your" front building boundary is wrong because it is pierced by the dead-end road in the original. That makes me doubt the diligence and thus the competence of the plan author and also the legal certainty of the plan.
Definitely seek professional advice from an architect or a local surveying office before signing the purchase contract.
