OP, we can't offer truly meaningful comments unless you post the complete airporty-by-airport itinerary. I do have a couple preliminary thoughts, namely:
1. It is almost impossible to book a complex itinerary on line. Most always they must be called in.
2. An open jaw is allowed at a stopover, but it can be difficult to book, particularly across regions. As others have noted though, you can't have three open jaws, and this itinerary does.
3. I would be concerned whether you can do this itinerary within applicable segment limitations, which are either four or five segments in each direction, depending on who you ask.
4. This itinerary appears perhaps overly ambitious. I question whether UA will allow you to book a North America-South Africa-Central Asia-Europe-North America award (even if you could squeeze it into the segment limitations). As someone else suggested, you may wish to look into a RTW award instead.