From Mahayana perspective, the Four Arupa Jhanas are before, not after the other four.
Of them, only the Sphere of Nothingness and the Sphere of Neither-Perception-Nor-Nonperception are of any real significance, while the first two are more like preliminary stages of the third.
The Sphere of Nothingness is the culmination of the teaching of Arada Kalama, Buddha's first teacher, who considered it equivalent to enlightenment. It is simply a state of consciousness empty of any content (incl. no perception of one's surroundings whatsoever). It is cultivated by progressively visualizing oneself in the center of city, then village, then camp, then empty camp, then empty field, then infinite empty space, then infinite consciousness, and then nothingness. Buddha taught it to some of his students as a preliminary practice. Cultivation of The Sphere of Nothingness is a good way to learn to control one's mind and get familiar with its workings.
The next level up is the Sphere of Neither-Perception-Nor-Nonperception, which a state of awareness that is not completely blank or empty, and does not involve complete blocking of external stimuli, but which nevertheless involves suppressing the associative function that normally leads to "recognition of particulars by their marks". Because of this, external stimuli are registered but not generalized to the level of objects. A perpetual example of this is looking at woman's curves and seeing only the raw visual with no trace of "woman" in the mind. Cultivation of the Sphere of Neither-Perception-Nor-Nonperception is a great way to get even deeper insight into the workings of one's mind at "microscopic" time scale, and it also helps with the practice of Guarding The Gates. Sphere of Neither-Perception-Nor-Nonperception was the culmination of the teaching of Buddha's second teacher, Udraka son-of-Rama, who considered it equivalent to enlightenment.
Both of these jhanas are outranked by the Buddha's own four jhanas, which are based on his insight into the nature of dukkha (Second and Third Noble truths).
The twelve nidanas of pratityasamutpada talk about emergence of phenomenal world, not so-called "objective" world.
Consciousness comes from name-and-form and vice-versa, because form is emptiness and emptiness is form. Consciousness is nothing but an interplay of forms, and forms are nothing but a content of consciousness.