The Shabbat Amidah has 7 blessings: the standard 3 opening praises + 1 middle blessing about Shabbat (replacing all 13 requests) + 3 closing thanks.
Question 2
Why are personal request-blessings removed on Shabbat?
Shabbat is a day of completeness and rest. Asking for things you lack contradicts the spirit of the day. The middle blessing becomes pure Shabbat-praise instead.
Question 3
What are the four different themes of the Shabbat middle blessing across the four services?
Each Shabbat service's middle blessing emphasizes a different aspect of Shabbat: Maariv=creation, Shacharit=revelation, Musaf=Temple service, Mincha=a more spiritual/mystical dimension.
Question 4
Where is Havdalah inserted in the Saturday night Amidah?
Havdalah is inserted into Atah Chonantanu, which is within the Atah Chonen blessing (wisdom). This insertion formally marks the transition from Shabbat to weekday.
Question 5
You forgot to say Atah Chonantanu (Havdalah in the Amidah) on Saturday night. What do you do?
Atah Chonantanu is ideal but not strictly required. If forgotten, the prayer stands. But you may NOT do weekday activities until saying Havdalah over wine.