How to determine if stepper motor will turn clockwise or counter clockwise initially
The answer is literally in your own picture.

If you follow the sequence in the diagram downwards it will rotate forward, if you follow the sequence upward it will reverse. What is forward and what is reverse, well, it may or may not surprise you that not all motor manufacturers agree on that, but I'd suspect most would say forward is clockwise.

As for your own example, what happens in that case is just heat, because a stepper motor only rotates because of a series of pulses like in the diagram. Which way it will rotate when you go to the next step, depends on whether you follow that up with a + on 2a or on 2b.

And as a side note, generally if you make up your own sequence that doesn't fit the motor's diagram it'll whine, buzz and heat up more than actually move.