for the good order: the tapu of the land could be transferrd at any time. Povided it is ARSA and it has passed the Militay Approval from Izmir (for Tarla it is somehow different, involving Turkish Ltd,...)
As soon as the building is finished (the owner of the tapu is also the owner of the house on it) the constructor has to prove to the belediye that he has paid all his social securities for his workers and his mandatory insurances during construction works.
This proof is issued by Mugla, and based on that paper, the belediye will give the iskan (living permission) and then you (actually the owner of the land) have to go to the tapu office, show the iskan ( which proves that everything is okay and done according to the building regulations) to have the house registered on the land.
Somebody will come to the plot and make a statement about that.
Afterwards you (again the owner) has to go to the belediye again to register (with your newly issued tapu)the house there as well, and that is when the belediye calculates the value of your house (based on the iskan) for tax purposes (your annual property tax).
If you did not transfer the arsa at any point during the construction, and it has not been done yet, that means that you now have to transfer a house to your name, which could mean that some of the steps I mentioned before will not be applicable to/done by you, but also by the constructor, if he is still the owner.
Still no reason to worry, because so far he has been paying for all the registration costs then.
The catch will depend on your contract: does it stipulate that you buy a house of him, or that he builds FOR you.
Probably, your contract will say that you buy a house from him, for the very simple reason, that there is money to be saved by the constructor, if he -in some way can declare- that the house is not bigger than 150 M2. Let me explain: if the house is not bigger than 150 M2, only 1% KDV is payable.... Maybe all of this is getting far too complicated. But if the constructor can get 18% KDV from you in the price offer he gave, and only declare 1% because of size, he stands to pocket the remainer 17%....
So, that is why most of the time, you will buy a house instead of building yourself, and that is why the constructor will go thru all the strouble of registering himself.
If you are still not clear about some things, feel free to ask. Sorry for this long comment, but this is Turkey, and nothing is explained easily (nor is it easy!!!)
One last thing: the ministry of forest and agriculture is working hard (especially in agricultural areas as also Üzümlü is, to prevent building on Tarla... But, as I read from your first post, you declare that it stipulated ARSA on the TAPU (did you see the original Tapu, and if so, what colour was it?)