What are the safety and effective parameters of Candela laser hair removal of the bikini area? I’m skin type 4. (photo)

It looks like the laser used to treat your skin was too warm for your skin type. I'm terribly sorry that happened to you.
 Laser hair reduction lasers work by seeking a pigmented target. The device is tuned by the provider to find the hair follicle. In your case, the laser found the pigment in your skin, hence the discoloration seen in the photos.
Generally the discoloration that you showed in the photos will go away on it's own. If you want to speed the resolution along you can use a Hydroquinone product on the area nightly. Your laser provider should be able to recommend a product to you. 
Candella is a laser manufacturing company and has a few different devices on the market. For skin types 4, 5 and 6 Candella's yag laser the preferred device.
I would suggest working with your laser hair removal provider closely on future treatments. There are a number of factors that contribute to hyperpigmentation such as this including tan skin on a patient. A partnership between patient and provider is necessary to determine the correct device, skin type and adherence to provider instructions for successful treatment.
Good luck on your aesthetic journey.