Question

How do Hally’s memories help advance the plot?

Answer 1

They allow the audience to learn about his past and his internal conflicts.

Step-by-step explanation:

Answer 2

It's because hally's intensely personal family issues become a reflection of how he was raised and explain why he treats Sam in such a demeaning and discriminatory way.

Including another reason why hally perhaps cannot understand is because he experienced the day in the park from a privileged position he has been in all his life--a privilege his race has afforded him. Hally has never been barred from any public space; he has never not gotten WHAT HE WANTED from Sam and Willie. By that Sam's experience of this happy memory for Hally is tainted by his exclusion from it since he was not allowed to stay with Hally.