Do the two eye patches on back of angry cobra hood deter animals from attacking it from the rear?

Eye spots have evolved independently in many unrelated animals. For example, butterflies, fish, and the cobra. So, yes they are effective in deterring attacks. One way to determine whether a feature is adaptive or not is to find out how universal it is. If it is not adaptive then random mutations that disables the feature will not be eliminated and as a result, there will be variation over time. Some individuals will not have it and still continue to live to pass along their genes without problem. if it is adaptive then virtually all individuals within a population will have it.

We see this in other snake species. For example, the ground snake (Sonora semiannulata) is highly variable in coloration, so variable that scientists used to think that there were several different species. Since this species is nocturnal, and since animals cannot see color at night, all the color patterns of this snake became adaptively neutral, since no particular color pattern will provide a survival advantage for its owner over other color patterns. So, if a mutation happens that changes the color pattern, it will have no effect on survival and as a result many different patterns will be passed along to future generations. In contrast, many snakes, e.g. garter snakes, can often be identified by their color pattern to the level of subspecies.