Yes, you will need this cable (or equivalent) for using CHIRP to program your radio. Just make sure that once you configure the computer to the cable you need to use the same USB port every time you connect the radio to the computer, and to turn the radio off before connecting.
Yes, this is the cable you need to program the BF-888S and all Baofeng and Kenwood radios.
If you run into a problem, go to http://www.miklor.com/BF888
There you will find current Drivers, Software and a Readable Manual.
Yes it works with Macs. This appears to be a genuine Prolific chip/cable. My PC recognized it with no "yellow triangles" and the Mac worked fine once I used the right driver. Go to: http://www.prolific.com.tw/US/ShowProduct.aspx?p_id=229&pcid=41 and download the genuine driver: md_PL2303_MacOSX-10.6up_v1.5.1.zip. Be sure to follow the old driver uninstall instructions in the readme. Then install the package and then look again in the driver directories identified in the readme to be sure the Prolific drivers installed. Then install Chirp, and make sure you install the Python runtime that Macs need for Chirp.
What is a Cobra Channel 11 radio? Is that GMRS? FRS? MURS? The compatibility of radios depends on the frequencies. The UV-5R+ is a VHF / UHF Radio. If it is GMRS you can type in the frequency or use the cables. If it is an FRS frequency it is illegal due to the maximum output requirement at a half watt and I would recommend against that. If it is MURS just have the power always set to low. You do not need the cable for any of this but I recommend it. You would need to use a software like Chirp to do it. You might have to also play with the tones to figure out the correct tone if they have one in.