and then you have to provide me from Quran that following a wrong Imam Mahdi is kufr.
Reference from 1st Khalifa's history (Hz Abu Bakr r.a) regarding false Mamoor is already provided in previous post. you never touched it.
but how would us accepting the imam mahdi make us kafir? Please clarify.
this is a wrong way of puting the question.
This is the correct way:
Question: how would us accepting (FALSE) imam mahdi make us kafir?
Answer: Becase he is FALSE; If you bellieve in a false one, you will become kafir. despite the fact you believe that he was not false. your believe will not be consider. and this phenomena is very well explain before with lots of examples.
you are still not allowed to issue your fatwa or even say that ahmadis are kafir until and unless you prove Hazrat mirza Ghulam Ahmad (AS) as the false Imam mahdi ..
May i ask, from where your 2nd Khalifa got the permission to issue a statement (fatwa) of Kufr against those muslims sects who dont believe in Mirza as Mamoor from Allah. If He feels that he is allowed to issue a fatwa or even if he says that Muslims sects are kafir then I and other Muslims do have the right to say that Mirza and his followers are kafir.