Contradiction in khilafah hadis? (Sahih Muslim Book 33, Hadith 10; In-book reference)

I found so many hadis on khilafah that contradict each other: > The khilafah after me is thirty years, then there will be biting > kingship in Sahih ibn hibban Khilafah is thirty years >I went with my father to the Messenger of Allah (may peeace be upon him) and I heard him say: This religion would continue to remain powerful and dominant until there have been twelve Caliphs. Then he added something which I couldn't catch on account of the noise of the people. I asked my father: What did he say? My father said: He has said that all of them will be from the Quraish. http://sunnah.com/muslim/33/10 Twelve khalifs last more than thirty years > The Prophethood will remain amongst you for as long as Allah wills it > to be. Then Allah will raise it when He wills to raise it. Then there > will be the khilafah upon the Prophetic methodology. And it will last > for as long as Allah wills it to last. Then Allah will raise it when > He wills to raise it. Then there will be biting kingship, and it will > remain for as long as Allah wills it to remain. Then Allah will > raise it when He wills to raise it. Then there will be tyrannical > (forceful) kingship and it will remain for as long as Allah wills it > to remain. Then He will raise it when He wills to raise it. Then there > will be a khilafah upon the Prophetic methodology. Then he (the > Prophet) was silent. in Musnad ahmad ibn hanbal Khilafah will be gone then come back. how do we understand them??