2. 10.8V and 11.1V are compatible, they are in common use.
3. the 10.8V(=11.1V) and 14.4V(=14.8V) are the different voltages, they are not compatible, please choose the right battery(Voltage) for your laptop.
4. The 7800mAh(12 Cell) battery will extend out about 1 inch from the bottom of the laptop, bigger size but help cooling.