1. Gram Panchayats have the power to approve layouts and residential properties within the boundary of their village The rural development and panchayats have been granted permission by the government to approve layouts/residential properties that are within one acre of land within the village boundaries.
You can verify the documents which bears the approval of the authority.
2. If the gram panchayat observed the rules laid down, then the approval for layout cannot be termed as redundant.
3. You are confused by various terms in this process.
Did you see that BBMP has approved the layout or whether the gram panchayat approved the layout.
You better refer the documents to an expert lawyer in the local and obtain a proper legal opinion and also get all your doubts clarified in person.
4. Where did you find the word 'unauthorised layout', do you have any documentary evidences to show that this was an unauthorised layout?
5. The details furnished by you are incomplete to render a proper legal opinion, hence you may produce all the relevant papers before an advocate in the local and obtain a proper legal opinion on all the subjects where you seek clarity.