Sunni’s consider all the Shia Imams (ra) very pious, worthy of honour and very knowledgeable especially upto Imam Musa kazim (ra).
Imam (ra) Abu Hanifah studied for two years under Imam Jaffer Al Sadiq (ra) and his father (Imam Jaffer’s) Imam Baqir (ra).
Imam Malik ibn Anas (ra) also spent sometime studying under the guidance of Imam Jaffer Al Sadiq (ra).
In fact the mother of Imam Jaffer Al Sadiq is the great grand daughter of Hazrat Abu Bakr Sadiq (ra) throuth his his son Muhammed bin Abi Bakr! [Muhammad bin Abi Bakr was brought up by Hazrat Ali (ra).]
Imam Abu Hanifah (ra) and Imam Malik (ra) also took knowledge from many other reputed scholars of the time.
Imam Abu Hanifah (ra) and Imam Malik (ra) are the best known students of Imam Jaffer Al Sadiq (ra).
At this time there were no religious differences as such among Muslims - as it is now. The differences were only on political level.
It is recorded in Shia books that no Shia Imam ever cursed any of the Sahabahs but had great respect and praise for the Sahabah. In fact the following is the sayings of the revered Imams.
Ja'far narrated from his father, Mu ammad al-Baqir, that a man came to his grandfather, Zain al-'Abidin, and said, "Tell me about Abu Bakr!" He said, "You mean as-Siddiq?" The man said, "How do you call him as-Siddiq when he is against you, the Family of the Prophet (s)?" He replied, "Woe to you. The Prophet (s) called him as-Siddiq, and Allah accepted his title of as-Siddiq. If you want to come to me, keep the love of Abu Bakr and 'Umar in your heart."
Ja'far said, "The best intercession that I hope for is the intercession of Abu Bakr as-Siddiq (ra)." From him is reported also the following invocation: "O Allah, You are my Witness that I love Abu Bakr and I love 'Umar and if what I am saying is not true may Allah cut me off from the intercession of Mu ammad (saw)."
About the twelveth Shia Imam, Sunni’s believe that he was not born, as the 11th Imam Hassan Al Askari (ra) died without any issue.
All the Shia Imams (ra) though being a great source of knowledge among other many notables have not written any books on Fiqh or other Islamic Sciences.
Fiqah Jafferiyyah though attributed to Imam Sadiq (ra) was not compiled by him.