Tax audit

Section 145 states the applicability of AS----however, it says 2 follow only two AS 

AS-1-----same as AS 1 issued by ICAI

AS-2---Same as AS-5 issued by ICAI.

It means if any firm or company follows just two AS then should we assume that the company/firm has no irregularity.

I have one book on tax audit, according to that book, the assessee should follow all AS ie 1-29.

i m confused whether the same is applicable for firm also.