Legal question about Real Estate and Protocol zdawczo Odbiorczy, help

We bought an apartment in 2005 from a dishonest and incompetent developer and are still waiting to enjoy it.
We still have a final payment to make and the final purchasing document to be signed at the Notary and the flats inside the building have walls and there is water and electricity in the building.
The question is : is it possible and legal to have the inventory of fixtures( Protocol zdawczo Odbiorczy) and start the works we want to start in the apartment before the final payment and the signing at the Notary?
We rejected the developer's equipment which is really crappy and intend to put nice and good quality paint, tiles etc..
The developer agreed to let us start the works inside ( wooden flor, tiles etc) everything we wanted actually which gave us second thoughts about the legality of this procedure in Poland and the risks.

Is it something common in Poland ?
We have asked around us but no one seems to really know.

We would greatly appreciate any help or legal advice regarding this matter.
Thanks a lot.

Am I missing something? You would like to paint / tile / floor an apartment that does not belong to you (as you have not signed a final purchase document).

I am sure that it must be legal, but certainly not wise. (you can paint and tile my house as well, no problem). What if something were to extensivley delay the hand-off of the apartment? What if someone were to destroy / damage your new installations prior to hand-off.

Right now you have the upper hand in this. You owe the developer money, and he is not getting it until he delivers the apartment/building to you in the spec agreed in the contract. Once you start throwing your own, un-recoverable, cash into the Developer's Apartment you are at a serious disadvantage.

Well we have already payed more than 85 % of the apartment . Plus the developer will owe us money ( or deduct it from what we still owe) for his equipment we don't want because we prefer to buy our own.
It was just a way of getting started in the renovation work because we are so tired of waiting but it is better to know if it is common or not in Poland to do so.

Thank you anyway for the info about the risk of damage or our new installations prior to hand off.
That's right , better to be cautious.