Now IOC1, IOC2, IOC3, FOC and all others are something which you will not find in case of other forces. There may be just an IOC and another FOC. The thing is, untill and unless you are testing it, its a prototype and designers and producers are responsible for it. Once all the testing is been done, then tweak it to the minimal user configuration to get the Initial Operation Clearance to get a squad or two inducted for user evaluation. Then come the final tweaking and rigorous testing of the whole system for Final Operation Clearance where final changes are made generally in software part for its full and final induction. Any sort of structural changes are dealt with in IOC only when it is not been sent to active duty. When you are purchasing a system from foreign OEM, then there is nothing like IOC or FOC to ask about. You have to take what you are offered and there might be some changes in it as per user requirement. But no one is going to give you a fighter as per your exact requirement. Just like the case of MKI's. It had been delivered only with custom software changes to accommodate our existing weapon system and there was no structural changes to it. Even now, to accommodate Brahmos, we were able to carry out the specific structural changes only after go ahead from Sukhoi.
Now in case of Tejas, three different IOC's are only to delay the induction as per my thinking. No one would go for such extensive trial on a prototype before going for FOC.