Theories about rank 10
Now there's a lot I want to say about rank 10 and what it means but I'll initially begin with immortal essence. From rank 1-5 and 6-10 there is a pattern between essence where the colour match (green copper to green grape etc.) In order to continue this pattern, then rank 10 must have some sort of purple immortal essence stone with potential fruit being passionfruit, plum (the one I feel most likely) and dragonfruit.
Moving on, the question becomes the requirements needed and what needs to be done in order for a person to reach rank 10. I personally don't believe that a person needs sgm attainment in all paths as it's on the same level as saying that a rank 6 gu immortal needs 10k dao marks to become rank seven (all because they can fight a rank 7 doesn't mean they are one.)
Instead, I want to analyse the requirements needed to reach other ranks first. Given that rank 10 is on the latter half of the power system it is much more likely for follow the conventions of the previous 4 ranks which require a person to undergo tribulations and after passing enough, their immortal origin core (I forgot what it was called but it was mentioned when referring to lang ya blessed land) to go up to the next rank. For rank nine, it was different. However , the gu immortal had to gain sgm in their path and be granted permission by heavens will to become it's dao master.
Throughout all ranks however, there is one underlying rule being that all of them must face a corresponding tribulations (heavenly tribulations, grand tribulations, myraid tribulations and heavenly calamity) so now the question it what is required to cause heavens will to create a tribulations needed for a verneable to reach rank 10.
Moving aside from that is dao marks, which is only really relevant at rank 9 where to become a verneable one needs 300k dao marks in their respective path. I personally believe that the requirement now will be for a verneable to refine all dao marks of their path in the world.
When Paradise earth's inheritance was talking about the 3 requirements to become a verneable (the heavenly calamity, 300k dao marks and sgm), the third condition is the most unique where a gu immortal must be recognised by heavens will who grants it permission to be the dao master of a path. My main theory for rank 10 is that in order for a verneable to reach rank 10 is that they must directly steal that paths and all knowledge of it from the great dao and henceforth heavens will then accomidating it into themselves (immortal aperature) becomming the literal embodiment of that path. Compared to before, where they were granted permissions by heavens will to use the path they are now the sole owners of this path (imagine the difference of buying an online game to play compared to buying the source code of the game to play.)
As a result of this, it would serve as the catalyst for the final tribulations where heavens will uses all of its might to stop you from basically ripping a part of the gu world for yourself fulfilling all the 3 requirement for rank 10 similar to rank 9 (tribulations, dao marks and extra unique factor.)