a) Rebecca's reaction: "and she sank back in the carriage in an easy frame of mind"
Amelia's reaction: "Miss Sedley was almost as flurried at the act of defiance"

b) Rebecca: satisfied, relaxed, proud, defiant.
Amelia: nervous, worried, frightened.

Es. 2
a) "So much for the Dictionary; and, thank God, I'm out of Chiswick."
"I hate the whole house," continued Miss Sharp in a fury. "I hope I may never set eyes on it again. I wish it were in the bottom of the Thames, I do; and if Miss Pinkerton were there, I wouldn't pick her out, that I wouldn't. O how I should like to see her floating in the water yonder, turban and all, with her train streaming after her, and her nose like the beak of a wherry."

Reasons: "For two years I have only had insults and outrage from her. I have been treated worse than any servant in the kitchen. I have never had a friend or a kind word, except from you. I have been made to tend the little girls in the lower schoolroom, and to talk French to the Misses, until I grew sick of my mother tongue."

b) Rebecca listens silently the friend's venting. She is very scared and worried, unlike Rebecca, for the act. She appears as a passive girl, submissive and she is very concerned about the consequences that may have the words of Rebecca, for example, when she says "Vive la France" that, at that time, was regarded as a blasphemy in England.

c) Rebecca: revengeful, passionate, impulsive, authoritarian
Amelia: gentle, simple, calm, submissive, conformist, passive

Es. 3
a) The narrator is a voice outside the story.

b) In lines 11-18 the narrator speaks of an episode to explain how the youth terror can torture people for a long time. The narrator tells of an old gentleman of 68 years who still dreamed of being flogged by Dr. Raine. The narrator explains that the man was still afraid of Dr Raine like when he was 13 years old.
I think it can be a possible justification for Amelia's action, to explain how as fears youth can continue even when we are older.

c) I think the adjective "heroical" is used ironically. Rebecca's act is not heroic but, in that time, it can be considered 'revolutionary'

and certainly unusual and unconventional.

d) The reader doesn't appears free to judge the characters: he can read only what the narrator chooses to tell.