In all drone filters, you cannot do stacking. 

Yes, this CPL Filter is only suitable for air 3. 

No, 2 filters fit. 

Hi, that's a good question. The Autel Nano plus is without a doubt more powerful and more cost-effective than the DJI Air 2S. Let's compare the two models in the following ways: Portability: The Autel Nano plus is a 249g ultra-lightweight mini drone with a 4K camera that is only 42% lighter than the DJI Air 2s, making the EVO nano plus more portable and easier to carry. Night Vision Quality: The Autel Nano+ drone uses the latest advanced RYYB array, which absorbs 40% more light than the Air 2S. The DJI air 2s still uses the traditional RGGB design and is definitely not the opponent of the nano plus drone. Under the same lighting conditions, the picture quality of evo nano+ is clearer and the details are richer. Flight Capability: The Autel EVO Nano Plus drone has a maximum flight altitude of 800 meters, while the DJI Air 2s can only reach 500 meters. Autofocus capability: The DJI Air 2s only supports Contrast Focusing (CDAF). The Autel EVO nano+ drone supports dual autofocus and can support phase-phase focus (PDAF). This ensures that the Autel evo nano plus beats the DJI Air 2s in dynamic object tracking. 

Hi, this is a multi-fuctional nd & black diffusion 1/4 filter 2-in-1, so it couldn't be seperated, you can order a single black diffusion filter, thanks.