“So there was a continuity, it was the same individual, from the time he saw Dipankara Buddha, till the time he got enlightened under the Bodhi tree.
What was it which remained same throughout that period?
Is it the same Gandhabba undergoing slight modifications but still the same.”
Consider a river. A river consists of a flow of water particles, that are in constant motion. The water level on one spot might differ from the water level on another spot, as well as changing at every spot all the time.
That might be an analogy of the “energy flux” that makes up a Gandhabba. The qualities of that flux depend on condition, just in the same way that the water level on one spot of the river depends on conditions (how much it rained, whether there are dams build along the river, time of the year).
So in one way, there was nothing the same between the phenomena we call “the Bodhisatta” at the time he met Buddha Dipankara and when he himself became a Buddha. But any lifestream, through the thoughts and abhisankharas created, conditions it’s future shape and qualities.
A river that was once a big river can become just a small dirty flow of water, if the appropriate conditions start appearing. In the case of a river, the nature or man can make these appear by using extensive amoubts of water, chemical factories, and so on.
In the case of the lifestream, the current phenomena can condition future phenomena. Whatever habits and intentions “you” cultivate will grow, and that is how the Bodhisatta grew in the journey of co pleting his qualities.
But as it is in the case of the river, where is the “river” itself? It is only a name for a number of causally interconnected phenomena, which themselves are arising because of causes and conditions being present, and generating new upfollowing causes for future phenomena.
A river is not the same feom one moment to the next, but it is also not “something entirely new”.
That would be my contribution to your question. I hope, it can be helpful.