Invoke the extended period of limitation for the financial years 2017-18 and 2018-19 - Goods and Services Tax - GST

Respected Sir, I require your valuable opinion on the below-mentioned issue. One of my clients has executed a works contract for canal works, serving as a sub-sub-contractor for the F.Y 2017-18 and 2018-19. Moreover, the department initiated an audit in June 2023, covering the period from April 2017. Below are the specific details of the works contract: Below are the details of the works contract details; He worked as a sub-sub-contractor within the project. However, he incorrectly claimed a sub-contractor exemption, charging 5% instead of the required 18%. My questions are: Can the department invoke the extended period of limitation for the financial years 2017-18 and 2018-19, despite the audit commencing in June 2023, and no Show Cause Notice (SCN) being issued within the normal period, i.e., by December 31, 2023? If a demand is raised for the F.Y 2017-18 and 2018-19 under section 74 of the GST Act , can we contest it since there was no suppression of facts? The sales details were already submitted in GSTR-1 to the department and were also provided to the audit party in June 2023.