What is the form of the opening "Allahu Akbar," and must the hands reach or touch the ears when saying "Allahu Akbar?"

It is authentically established in Sahih (definition) Muslim that the hands should be raised level with the shoulders at the time of the opening takbeer (takbeerat al-ihram (definition)). The description of this raising is that the fingertips should be level with the earlobes, the thumbs with the lower part of the ears, and the palms with the shoulders. This raising is a Sunnah (definition) (recommended act) and is mustahabb (desirable) by the consensus of the Ummah. As for the opening takbeer, saying "Allahu Akbar," it is obligatory, and the prayer is not valid without it.