ALLOWABLE DEDUCTIONS IN APPEAL TO CIT(A)

if assessee have 3 businesses A, B and C and appeal was made by assessee to CIT(A) for addition made by AO in businesses A and B , then could the expenses unclaimed in the return be claimed now for business C against CIT(A).

Would there be any difference if those expenses were disallowed by AO u/s 143(3)?
Also could unclaimed deduction u/c 80C be claimed at CIT(A) if not claimed in return?