RACH preamble 5G NR

Hello everyone.
I have number a questions about RACH preamble.

  1. What is the size of the RACH packet received from the UE towards the gNB?
  2. Is the PRACH process included in the RRC layer?
  3. Is there any RRC messages for this process? And if so, what are the messages?
    I would be happy to receive your help.
    Thank you and good day.