First off, let me say how jealous I am you live in Singapore. My in-laws live there, so I get there once every couple of years. In other words, not nearly as often as I would like.

If you are looking to use CO miles, I suggest taking a peek at the new travel and upgrade award chart on CO.com: link

You certainly can use CO miles for SQ flights, provided you aren't trying to book premium class travel on certain aircraft, such as the 777-300ER, A380, and A340-500. On the non-stop SIN-JNB flight, this isn't currently an issue, as it is operated on a 777-200, which offers the regional premium class product.

You can also use CO miles to upgrade from coach to business, or from business to first, using the miles listed in the above chart, assuming there is upgrade space available and if you've booked in the correct fare class. In coach, this is Y/B and in business, C/D. More info here: link

For availability, you can always use the ANA or the KVS tools, either of which are easy to find via the search functionality. Personally, I prefer the KVS tool, as I find it easier to navigate than the ANA website. YMMV.
Good luck!