Sir, although it has not been much time in practice. Pardon me if there are any faults or misconceptions of my concepts. I would like state following as a personal opinion over your questions:-
1) Is it illegal to file a reply affidavit by an officer other than the Respondent? If so under what law?
Here in Rajasthan High Court, whenever any affidavit is filed, usually the same starts with the terms decalaring under what capacity he is filing the reply... For example : I, XOX(name) s/o YOY(Father's name) Age DD, DESIGNATED AS do hereby state under oath that....
So, it is usually presumed that the person who is filing the affidavit is under the authority to file the reply or affidavit, whatsoever.... In case you will raise this objection through any explicit averment by way of rejoinder or additional argument, then as you said, they may respond accordingly. Instead, why dont you raise it first at the time of argument in the most authoritative way by bringing the attention of the Hon'ble Court at the page of sworn affidavit. Along with that, be ready with some case laws that the person who has filed the affidavit is not in the capacity and case laws regarding punitive measures for misleading the Hon'ble Court...
2) Can a contempt petition be filed against the Respondent, the other officer who filed a reply affidavit and the lawyer representing the respondent?
The Contempt petition can be filed only for non-compliance of the order or directions of Hon'ble Court. I suppose, since there is no standing order or directions explicitly which has not been complied with. Moreover, if your writ or matter is already pending then how come you can file a contempt. so, its not possible. Against a lawyer, the contempt can not be filed at all because whatsoever the case may be, its impossible that Court passed any direction against the concerning lawyer which he was obligated to follow..
3) What remedy other than the contempt petition is available for false statements in affidavit? (This might be only against the signatory to the affidavit)
Contempt per se cannot be filed unless the matter has been decided and there was the order which was not complied with. In case, there was any order for which the concerning public officer was bound to follow, which he has failed to follow, contempt cannot be filed. If this is a case, where court disposed the matter with a direction and the same was not complied with, you can go with the contempt proceedings...
Adv. Ravish Sharma