NR PRACH queries related to configurations and parameters from spec 38.211

Hello 5G experts,

I have few queries related to PRACH NR configurations and parameters related from Spec Could you please help to answer for the same So that it would be great help.

  1. Why there is sub carrier spacing allotted for PRACH channel alone ?
  2. How the parameters Nu and Cp contributes to different PRACH formats ? What are the different use cases related to these
  3. What are the use case for four different preamble lengths
  4. Why the sequence number to logical root sequence are mapped and shuffled ? In what way the sequence are mapped to logical root sequence index ?(in 38.211 Table and Why no mapping for 838 logical root index ?
  5. Why the mapping of logical root idx and root sequences are different for LRA = 139 (38.211 Table
  6. Why NCS values are not defined for restricted types with zeroCorrelationZoneConfig values (14 and 15) ?