so far I know if matter goes in appeal than  matters referred in appeal cannot be revised u/s 264

mr gopal is right- beacuse the matter which has gone an appeal become merged and cannot be revised.

But as u as per section 263, if appeal made to CIT(A) on certain matter

than on some other matter CIT can revise the order of AO u/s 263

I m not very sure but it can be because of in sec 263 -concept of Partial merger is followed.

and in sec.264 concept of total merger is folowed.