Defamation

No. You must be defamed publicly and your reputation must be affected in eyes of your peers after they get to know what allegations have been made against you. although, the complaint is made in public forum, yet it is a private complaint and hence it will not amount to defamation.

 

Yes you can file defamation case under section 499 under such circumstances. Because complaint itself is the cause of action for your case. Filing such complaint destroys your reputation in the eyes of your family, your friends and your colleagues.

Yes, you can in case your reputation has been affected.
Defamation is an action of damaging the good reputation of someone, it may be verbal or in written form. It may also be through signs or any other form of visual representation for harming a person's reputation. In IPC, it is defined U/S 499, IPC, 1860, which defines it as injury to the reputation of a person resulting from a statement which is false.  Section 500, IPC, 1860, provides punishment for the same.

whether it is criminal case or complain case