Coming out of PEO and wants to set up new plans

Hi

All below are on a calendar basis. I have never seen this before. Hope there are some out there who have experience/knowledge on this.

Company X left PEO on 10/1/2022.

They want to set up a new combo plan for 2022 which will be 401k/PS plus CB.

How are the PEO contributions and salaries applied? How is testing done, just from 10/1/2022 (salaries and contributions)?

Are they supposed to be short plan years?

Anything else i need to be aware of?

Thank you in advance.