The analyses of a text #2

The narrator recalls his adolescence.
He came to his old nurse Peggotty's hometown Yarmouth to meet Peggotty's nephew Ham.
He is having a tempest.

Chapter 55 TEMPEST
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As the receding wave swept back with a hoarse roar, it seemed to scoop out deep caves in the beach, as if its purpose were to undermine the earth. When some white-headed billows thundered on, and dashed themselves to pieces before they reached the land, every fragment of the late whole seemed possessed by the full might of its wrath, rushing to be gathered to the composition of another monster. Undulating hills were changed to valleys, undulating valleys (with a solitary storm-bird sometimes skimming through them) were lifted up to hills; masses of water shivered and shook the beach with a booming sound; every shape tumultuously rolled on, as soon as made, to change its shape and place, and beat another shape and place away; the ideal shore on the horizon, with its towers and buildings, rose and fell; the clouds fell fast and thick; I seemed to see a rending and upheaving of all nature.
Not finding Ham among the people whom this memorable wind - for it is still remembered down there, as the greatest ever known to blow upon that coast - had brought together, I made my way to his house. It was shut; and as no one answered to my knocking, I went, by back ways and by-lanes, to the yard where he worked. I learned, there, that he had gone to Lowestoft, to meet some sudden exigency of ship-repairing in which his skill was required; but that he would be back tomorrow morning, in good time.
[David Copperfield by Charles Dickens]
1. I'd like to know if "undulating hills" refers to "billow."
2. I'd like to know if the subject of made" is "every shape."
3. I'd like to know if "its" refers to "billow."
4. And I'd like to know what "meet" means here.
Thank you in advance for your help.