Dear Shailesh,
Well I just found the solution, which I performed on my client and its working fine. First you need to go through following IMG path:
SPRO>IMG>PSM>Funds Management>Budget Control Systems>Availability Control>Define Activation of Availability Control
There Give your FM Area and make sure you select the check "Ignore Revenue Items"
This will ignore the AVC check on revenue posting and their reversal posting altogether and will not give you any information message as well, which you have set in your tolerance profile.
However, if you still wish to receive the information message defined in tolerance profile, then simply uncheck the "Ignore Revenue Items" check and maintain a derivation strategy to override the revenue items profile as mentioned in reply 1 above. This will make sure you can post revenue and their reversal without any FM AVC error.
Also remember the derivation strategy mentioned in first reply relates to tolerance profiles and you must not mix it with FMDERIVE.
Regards,
Amar Lal