I wish the Muslims should be united & do not divide into sects. How can we do so to be saved from dividing ourselves into sects?

Get the leaders of the sects to accept and/or allow the other sects to believe what they want.

But thus the issues, since in some cases, one sect does not even accept the other sect as being Muslim. Each side has to accept the beliefs of the other, which will never happen.

Same as in Christianity, one group of Christians, consider another group of the devil, so how would they ever agee to work anything out.