Ground-to-Cloud

Appears that ground-to-cloud is possible, though normally only a result of a man-made object creating "unnatural" electric potential, and is the least common type of lightning.

In your image above as well, you can see a lot of time is lost in looking for the route, whereas the return stroke just runs through the well defined channel and hence is much faster.

That the lightning roughly follows the field gradient explains the general direction. The feedback sustains the lightning once it has started. The explosive expansion of the heated air explains its chaotic parts.

When one of the pilot lightning branches gets close enough to the ground that an arc to the ground is completed there is a completely conductive connection between the separated charges which will lead to the runaway discharge known as a lightning bolt. (It's a runaway process because higher currents increase the arc's conductivity by turning more air into plasma, so the current grows until the charges are exhausted.)

I do not think that the eventual main lightning bolt has a different "direction" than the pilot lightning, and I cannot find observational evidence. Even at 100,000 frames per second the intensifying appears instantaneous, and the main bolt is so bright that cameras are overloaded.

It may appear to the human perception as a "back strike" because it starts once the pilot lightning touches ground, much like a bounce-back event. But I think it's just that suddenly a lot of charges flow where only few charges were flowing a millisecond earlier, in the same direction.

Furthermore one thing you should have in mind is that lightning is not just a static electricity discharge.

This discharge may produce a wide range of electromagnetic radiation, from very hot plasma created by the rapid movement of electrons to brilliant flashes of visible light in the form of black-body radiation. Lightning causes thunder, a sound from the shock wave which develops as gases in the vicinity of the discharge experience a sudden increase in pressure. Lightning occurs commonly during thunderstorms and other types of energetic weather systems, but volcanic lightning can also occur during volcanic eruptions. Wikipedia

Above is written that the discharge itself may produce wide range of electromagnetic radiation. The majority of that radiation should be produced once the Cloud To Ground path has been established. In case we do have a combination of positive and negative lightning on that path then perhaps a differently filtered view of this lightning (microwave, infrared, ultraviolet, or even X-ray range) would have been more enlightening.

I actually don't think that all the radiation comes from the discharge itself as written above. It should be a combination of static electricity and radiation even before the discharge, only to be amplified at the moment of discharge.

An even more peculiar case than Ground To Cloud lightning is also the case of Ball Lightning. This video shows something that could be identified as ball lightning. One of the theories on how ball lightning occur indicate that Si element on soil could be a factor.

EDIT

In order to prove my point on this optical illusion in the above image i add a link of another optical illusion, of course on that video the train has one and only course but we see it to have both, in cases like that the human brain finds other ways to determine the direction.