Dear Friend, This situation may be unnerving you, being removed from your core competency and put in an area where there is very little limelight or no light even. You could rightfully feel hurt, humiliated or insulted, your colleagues and peers would be adding to your misery. Now, the legal options which you have sought and available to you are:
1) What does your appointment order say, have you been appointed for only this specific work viz progressive accounting,finalisation of accounts,Balance sheet,Audit,MIS reports,Debtors and creditors reconciliation,preparing and reconciliation of cash and bank books,levy various states and central taxes it's reconciliation and filing of return etc.In that case you can have a case that the transfer is against the terms of your appointment.
2) As a result of transfer, has your status changed adversely, in terms of your position as HOD/HOS, or your salary or the eligibility for promotion etc. By transfer your service conditions cannot be changed adversely.
3) You have mentioned the transfer to be motivated or out of malice and has pointed out the prejudice of CFO, but do you have sufficient material to prove the same in a court of law, which requires evidence. Mind you, bias & prejudice could be easily alleged but proving is rather difficult.
4) The legal principle is that transfer is an incident of service and the courts are reluctant to interfere in them unless malice or malafides are clearly proved and the onus to prove it on the party alleging it. The balance lies against the petitioner in most of the cases.
You may evaluate your chances against the aforesaid principles and if you feel you have a very good case, then you may approach a competent advocate and try your chance. Further word of caution, if you are in private sector, litigation is not suggested in the matter.
Otherwise, take this opportunity as a challenge and show your capability and enthusiasm to work harder and prove your mettle. Or you may look for greener pastures elsewhere and looking to your job profile you have high value. In any case there shall be no regrets later.