1)
What is thie Pasuk coming to teach us?
1.
Refer to 15:24:1.1:1 and note.
2)
Why does the Torah mention the Ger here?
1.
Ramban: Because it is a sin that - due to their past - Geirim tend to transgress and cause others to transgress as well.
3)
Having already stated in Pasuk 25 that they sinned be'Shogeg, why does the Torah repeat "Ki le'Chol ha'Am bi'Shegagah"?