H1B Extension , Administrative Processing

My husband went for H4 stamping in Mexico. I have approved I 797 but not stamped in my passport. He was asked about stamped visa in my passport. We showed him the approval notice. VO went inside and came back after 5 min and asked him questions about his H1b . He recently had his H1b extension denial. He was asked about the denial reason. We didn’t have a copy of that as the employer doesn’t share that. I am not sure why they asked about his H1b extn denial.

He was given white slip and passport returned. How much time it normally takes in this case for H4 decision to come.

The employer is planning on starting his H1b extn process again. Is there something to be worried about his new H1b Extension petition that they are starting parallely. Can the administrative processing for H4 affect his H1b extn process too.
We are so confused and tensed.