US Immigration from Senegal

We just received the NOA 2 from USCIS approving the K-1 this week. I noticed on the NOA under Notice Type it reads the approval is Valid from 04/1/2025 to 08/13/2025. Can anyone provide any insight into this "valid from" meaning. From my understanding we are not able to access the claim to begin any steps in the portal until we receive the case number and other necessary information from NVC. We also need information from NVC to request an appointment date with the Embassy in Dakar. Does anyone have any insight on their current backlog for interviews? Also, what happens if we are not able to get the interview scheduled prior to August 13th due to backlog? Does the claim just expire and we have to pay to go through the process again? Thanks in advance for any insight on these questions above. Please note these are standalone questions and do not have anything to do with my "timeline" and/or the original case I submitted and setup my account for. Thanks again!

I received the NOA1 from CSC in March 2024, and am waiting for NOA2. If CSC if processing NOA1 to NOA2 from roughly 101 days ago, is this accurate? Considering our case would have been received more than 101 days ago.

I am looking for clarification for the K-1 process. Once USCIS sends the NOA2 showing the case was approved June 27, 2024, we now wait for NVC to contact the petitioner and beneficiary, correct? This is where I am confused, do we send documents to NVC for the K-1 to get a "documentarily approved" status, and then the case is forwarded to the embassy to schedule the interview. Or, does NVC just receive the case, assign the case number, and forward on immediately to the embassy where they then contact beneficiary and petitioner with the documents needed and interview scheduling procedure?

Does anyone know how the processing service center is assigned for an I-129F?