Imam Jafar stated Believing in Allah and Prophethood was Enough

The 12er Shia say that Waliyah was a condition since day 1. In fact, many of them even go far as saying the even 3 Calipahs first accepted the Waliyah, and then rejected it after the demise of the Prophet (sawas).

Now lets see what Imam Jafar says in the Dozener Shia ahadith book al Kafi.

Ali ibn Muhammad has narrated from certain persons of his people from Adam
ibn Ishaq from ‘Abd al-Razzaq from ibn Mihran from al-Husayn ibn Maymun
from Muhammad ibn Salim from abu Ja’far, recipient of divine supreme
covenant, who has said the following:
“Abu Ja'far, recipient of divine supreme covenant, has said,
Allah commanded every prophet to follow the path and the tradition. Of the traditions that
Allah, the Most Majestic, the Most Holy, commanded Moses to
follow was al-Sabbath. Those who observed its greatness and
did not violate it out of respect for Allah, Allah admitted them to
paradise. Those who violated its sanctity and considered lawful
what Allah had made unlawful and prohibited, Allah, the Most
Majestic, the Most Holy, sent them to hellfire for their making
fishing lawful. They captured fish and ate them on Sabbath.
Allah showed anger toward them even though they had not taken
anyone as partners of the Beneficent or doubted the truth of what
Moses had brought. Allah, the Most Majestic, the Most Holy,
has said, “You certainly knew about those among you who were
transgressors on the Sabbath. We commanded them, ‘Become
detested apes . . .’” (2:65) Then Allah sent Jesus with the
testimony that said, “No one deserves to be worshipped except
Allah and all that he (Jesus) had brought was from Allah.” He
made for them a system of law and a path. He abolished the
Sabbath for which they, before, were commanded to pay respect
and the ways and traditions that Moses had brought. Whoever
did not follow Jesus, Allah sent them to fire, although all that the
prophets had said was that no one must be considered as a
partner of Allah. Then He sent Prophet Muhammad and for the
ten years that he lived in Makka everyone who testified to the
fact that “No one deserves to be worshipped except Allah, and
that Muhammad is His messenger” Allah admitted him to
paradise just because of his affirmation. It was belief and
affirmation. Allah did not punish anyone of those who died
following Muhammad in that matter except those who took
partners for the Beneficent. Evidence of this is what Allah, the
Most Majestic, the Most Holy, has revealed in Chapter 17 in
Makka). “Your Lord has ordained that you must not worship
anything other than Him and that you must be kind to your
parents . (al Kafi, H 1506, CH 14, h 1)



From this we can see there was no divinely appointed Imamate in the Meccan rule. As for Madina, I don't have convincing proof against the 12ers Shia, as that will require more research. However, the refutation for the Meccan period leaves no room for the 12er Shia to make any suggestions that Imam Ali (as) was since  appointed since day 1 and believing in his divinely appointed Imamate was requirement.