Some key ideas i got:

Regrets and Realization: There is a notion that Ah Guan may have regrets about his relationship with Michael. The text suggests a parallel between Ah Guan's advice to Lizhi about relationships and family, and his own experiences with his son. Ah Guan's reflections and advice could indicate an awareness of his past actions and their impact on his relationship with Michael.

Tough Love and Its Consequences: The idea that Ah Guan's approach to parenting Michael might have been one of tough love is suggested. This approach, intended to guide Michael, might have been perceived by Michael as stifling, leading to a rift between them. The metaphor of the parent plant, used by Ah Guan in his conversation with Lizhi, might symbolize this aspect of their relationship – the need for independence and the potential harm of overprotection.

Individuality and Letting Go: There is a belief that Ah Guan may have come to understand the importance of recognizing and respecting Michael's individuality and the necessity of letting go. This is inferred from Ah Guan's philosophical musings and advice to Lizhi, suggesting a parallel to his own experience with his son.

Inconclusive Evidence of Realization: While there are indications of Ah Guan's possible regrets and realizations regarding his relationship with Michael, his lamentations and reflections are open to interpretation, and it's unclear whether they directly translate to a newfound understanding of his estranged relationship with Michael.