2400 m² plot. (according to the realtor building land would be according to the standard land value at €165/m²)
Can really everything be classified as building land because it can also be built on? As a rule of thumb, 800 sqm is considered building land for a detached single-family house and the rest is valued as hinterland/garden land. The rest then at 10-30% of the building land price.
How long is a building permit valid?
In Bavaria - I believe - four years.
Energy Saving Ordinance in terms of documentation, since insulation is not yet applied
If you now need a new building permit, you probably have to build according to the current Energy Saving Ordinance. That costs money today. It will probably also be insulated differently than originally planned. Recalculation, etc.
It was more about the principle of whether it makes sense to continue building a shell after such a long time and the influences of the environment or not.
Basically: yes and no - only an expert can answer that for you. And no, you have to take the money in hand first before finding out whether the project has a chance of success.