Do 4 batteries capable of outputting 0.5 A in parallel give the batteries a max output of 2 A?
If batteries are in parallel then the max output current adds for each battery.  For example if 4 batteries of 0.5A are placed in parallel then the total output current becomes 2A.

When batteries are put in series their output voltage adds but the current does not add.  For example four 1.5V, 0.5A batteries placed in series will give you a 6V 0.5A battery.

Batteries can be placed in combinations of series and parallel at the same time.  For example, you can make a string of eight 1.5V 0.5A AA batteries in series to make a 12V 0.5A battery string.  You can then place eight of those 12V 0.5A strings in parallel to increase the output current to 4A.  So you would need 64 AA alkaline batteries total.

Note that note that ordinary alkaline AA batteries generally have pretty high internal resistance (0.25 to 0.5 ohms).  They are usually not suitable for driving heavy loads.  NiMh AA batteries can have resistances of only milliohms and are suitable for driving loads of several amps.

From your post what you really need is a 12V battery that can output 4A for 1 hour (4Ah).

You can get a 12V 5Ah lead acid battery on Digikey for $27, which is probably cheaper than buying 64AA batteries.

BP5-12-T2    Battery, 12V, lead Acid, 5Ah

http://www.digikey.com/product-detail/en/b-b-battery/BP5-12-T2/522-1010-ND/653331

Please note that if two batteries are placed in parallel they must be the same voltage.  Otherwise one battery will try to charge the other.  In the most benign case it would mean that you loose some energy.  In the worst case the batteries could be destroyed or explode.

What this means practically is that you should only place identical fully charged batteries in parallel.  A discharged battery even if identical to another battery will have a lower output voltage than a charged one.