Ampere-hours, or amp-hours for short. It's a measure of the total energy that can be stored in the battery. A battery rated for 20 Ah can supply 2A for 10 hours, or 5A for 4 hours, or 20A for 1 hour.
the battery amp hour (ah) rating is what is important as long as the new battery has the same or higher ah rating it should be OK
Yes, it mAh or Ah is how long the battery lasts, it does not affect performance.
Yes
No, it does not have enough capacity (i.e. ah rating).
You really can't calculate that, it's determined at manufacture. It'll be stated on the battery casing. Look for something saying Ah, Ampere hours.
A 55 Ampere Hour battery is not recommended for your car. The recommended battery is a group 49, with 100AH and proper venting. Other sizes will not fit and incomplete venting is dangerous.
V is the batteries rated voltage. Ah is the amp-hour of the battery. This is a rating of how many amps it can supply for a given period of time. For example a 600 Ah battery with a 100 A load means that the battery should last 6 hours.
Yes. In about two to two and a half hours, depending on the condition of the battery.
That depends on the characteristics of the battery. The numbers you quote don't give enough information. 4 Ah is simply a measure of the battery's total energy storage (for rexample, 1 ampere during 4 hours, at the specified voltage), not of how fast it can be released.
Check and see how many Ah (Amper hours) your battery is. If it is for a gas/gasoline car, then it is probably around 42 Ah; batteries for diesel are usually around 72 Ah. Check the power of your battery charger. It should be something between 4-6 A. You must divide the battery capacity by the charger strength to get the time necessary. For example: your battery is 42 Ah and your charger is 6 A. Then the time needed will be 42 Ah / 6 A = 7 h. Charge your battery no longer than 7 h. Please note that overcharging the battery permanently damages it.
12 Volt 70 AH battery
First the maximum charging current for the battery should be checked. If that is unknown it can be taken as one tenth of the capacity, e.g. 2 amps max for a 20 Ah battery