Are all levels of the mind—conscious, subconscious, deep subconscious, and cellular consciousness—present during transition after death of the body, and also within earthbound spirits if there is a failure to reach heaven?

This is most definitely the case. Your consciousness takes many forms, operates at differing levels of your being, and has differing sources of influence given it is adapting to being a part of your life, as a physical being in an animal body essentially, one that is of the flesh. That does not mean that with transition those levels of consciousness will all come together, become unified, to better strengthen and inform the whole what has been going on with the compartmentalization to gain an understanding of the missing pieces held by another part of their mind. The fragmentation will still exist because it is a remnant of how the consciousness came to be impinging on the physical body and makeup as comprised from the pre-life planning, the soul attributes inculcated into the incarnate being, and the influences via DNA and the cultural connections through many, many cordings throughout history that will be a source of influence. So, in a sense, it is like the body has dissolved with the physical death but those layers of consciousness remain behind. They are still part of the soul as extensions but, for all practical purposes, are still segmented in ways to serve their prior functional roles within the physical incarnation, and thus are still in a state of incompletion, fragmentation, and disarray from having gained many adverse influences of wounding, suffering, and loss. And all of that karmic entanglement coming from other lifetimes will still be interconnected and impinging on the being, because the energy of karma is the energy of consciousness, and that is why karma can be so powerful, it talks to the being directly without a filter, so it does not go through the eyes and ears or tactile sensations of the body, it goes directly into the being and can influence multiple levels, particularly the deep subconscious. But with the ongoing continued fragmentation making the deep subconscious unreachable by the conscious self, it is much like having multiple personalities, some better informed but ill-equipped to make decisions and plan a way forward, and others just in the dark and not understanding even the dilemma of being dead. This is why healing is the answer for departed souls, and why so many need a divine intervention to raise them up fully, so they can cooperate with the light callers and return to the heavenly realm and not become stuck in limbo.