Community fees are only charged from the date on which you complete and as legally you cannot be forced to complete on a property where there is no Certificate of Habitation in place the again the community fees would not be liable for payment
The community charges are actually based on the date that you completed so if, as some people did on Mar Menor 2, you chose, because of the financial situation with Polaris, to complete before the COH was issued the you are liable to community fees form the date that you legally completed
The developer does have to declare any charges, mortgages etc on the property, at completion at The Notary and discharge these prior to completion, not just verbally but in writing as part of the process and your lawyer should also be checking this
If a property is complete, the COH issued and you have been notified of a completion date and you refuse to complete any claim made by a developer will include a claim for back dated community fees
Rememember that before charges are agreed and issued ther is normally the first meeting of the communidad and the appointment of the Administor who should actfor the owners to deal with these type of queries and agian I know that these meetings have happened at MM2
I hope that this information helps