If it does freeze, no. The ice would damage the plates/circuitry maybe even the case.
no, its not possible. Actually it is possible for the battery to freeze, if the charge gets low enough it will freeze.
Not good. Likely will require a replacement. The liquid in a car type battery is an acid that is pretty much freeze-proof under normal temperature ranges seen in most climates, as long as the battery is FULLY CHARGED. However, if the battery is discharged or in a low charge state, the electrolyte can freeze. A hard freeze will damage a battery and drastically reduce its capability to hold a charge.
Yes, this will prevent the clock from running it down. You can also install a trickle charger to keep it charged. A battery with no charge will freeze. Keep it charged and it will not freeze.
If you are using it to turn on the car a good battery would help.
you can avoid draining the good battery
Usually from being discharged in below freezing weather. The water will freeze in a dead battery, expand, & swell the battery. This won't occur with a fully charged battery.
if the battery is good and charged sure
yeah ;)
A car battery does not need a capacitor as it's regulating capacity (when in good condition) is well above any capacitor you can fit into your car.
If you don't keep an otherwise good battery charged in freezing weather it can freeze and break the case. If your battery won't hold a charge because something is draining it, you should disconnect a cable and charge it then reconnect it before you try to start the car...or fix whatever it is that is causing the draw. It is better to keep the battery charged so you can start the car when needed. Consider hooking a battery tender to the battery if it discharges because of long-term disuse.
my battery is good but having problems with starting
Get a donor car and use it's battery to start your car. You will need a set of quality jumper cables. Or you can charge the dead battery on the car for about 2 hours with a good 10 amp battery charger.