I think the terrible two's are a bit of a myth tbh. I think they go through different behaviour at different stages and ages. I'm sure it is just as tough at 5, 10, and 15 as it is at 2 but for different reasons? It seems to start once they are aware of how to get attention (good or bad)

Lolly was also an angel up until around 18mths and then she turned into a little madam almost overnight.
As has been said already, stay focused and stick with whatever form of discipline you are going with. I think changing it around just confuses them and they don't know where they stand. It sounds to me like you have a very normal toddler there hun, so try to not stress over it too much! Xx