No you can simply take a multimeter and stick it across the terminals to monitor the voltage and then touch the wires of a heavy load to the battery. If the voltage stays reasonably close to 12V then the battery is still good enough for that sort of load.
The load can be anything really. Resistors are a good load because they consume a predicable amount of current at a given voltage. But offten 12V car light bulbs are used as loads because the headlights typically are around 70W. For 24V truck ones can be used or two car lamps wired in series.
For really heavy loads there is a cheep trick of wire in a bucket of water. A few meters of thin wire can work as a load up to a few kW, but because that makes the wire get hot really quickly and might melt it. To prevent that you simply coil the wire up some and dunk it in a bucket full of tap water. The wire is more conductive than the water so the current will generally stay in the wire but the water cools the wire. Eventually after a few minutes the water would also get hot and might start boiling, but for testing batteries like this you only need it to work for 1 to 10 seconds. (Also this is more appropriate for very big batteries that weigh as much as a person)
As for trying to get the batteries working again, it is possible sometimes, but even if they do recover they will never reach full capacity again. Sometimes giving it a discharge and charge cycle helps them recover, other times sending huge pulses of current trough it can desulfate the cells and help them work again. But if the batteries are already really old its not worth bothering, at some point they simple run out of lifetime and die completely.
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