If the voltage is the same, the batteries are most likely interchangeable. The "mAh" rating simply tells you how much energy the battery can store - so, a battery with more mAh will last longer.
The rating mAh is a measure of the amount of energy that can be stored in a battery. The higher the number, the more energy can be stored. Assuming that the batteries are the same physical size and have the same nominal voltage, there is no reason why a 1400mAh battery shouldn't be used in place of a 760mAh. The only difference is that the larger battery will last longer between charges than the smaller one.
Yes
No, not unless you installed a 6 volt battery instead of a 12 volt battery.
If the light is still on then the problem was not the battery but was instead the alternator which is more than likely defective.
Alternative power sources that can be used instead of a battery include solar power, wind power, hydroelectric power, and fuel cells.
If it will physically fit in the space, then yes, the 2700 mAh battery should work fine.
the device may not work
The shaver will run a bit slower.
My question is why would anyone do this? But since you asked. It will ruin the battery.
no
A radio that gets power from batteries instead of the outlet on the wall.
Yes, you can use a 12V 7Ah battery instead of a 12V 12Ah battery, but there are important considerations. The 7Ah battery will provide a shorter runtime and may not meet the power demands of your device if it requires consistent output. Additionally, ensure the discharge rate is compatible with your application to avoid damaging the battery. If your usage exceeds the 7Ah capacity, it may lead to quicker depletion and potential over-discharge.