If you really want to know how to spot a fake iPhone in Zimbabwe I would suggest that you go with an open mind. Many-a-time people will just have it set in their minds that this phone is the one I want to get and won't take any advice.
Here's how to see that a phone is fake and you're being take for a rid:
1. price - be very careful of any device that is cheap, or the price is too good to be true. iPhones cost an arm and a leg and you are advised to check what the price of one in your area is before making a purchase.
2. touch and feel of the product. All iPhones run on iOS and are not android or java capable. check what kind of App Store is running on the phone. Usually best to go with a known original and compare and contrast.
3. charging ports is different. Check that it is 8-pin (for the latest iPhones) or 21-pin (for the older models).
4. Check if it has a memory card slot. Apple does not make it's devices with add on memory but they come standard with the phone. Trick the person selling it and ask them if it has a memory card, if they confirm then it is a fake.
5. dual sim functionality. Apple does not make dual sim phones and if the person selling it to you states that it has dual sim then run. Run fast. Run very fast.
Be all the more careful with the new iPhone 5S and/or 5C where people will be telling you that this is the new way that Apple is making them.