Which of the Disciples (originally named Simon) seems to have been closest to Jesus, despite a number of well-intentioned but impulsive blunders, and was given authority as 'the rock on which I shall found my Church'?

A Christian is a person who lives their life according to their belief in God and Jesus. They will accept the Biblical stories of His life, teaching, ministry, sufferings, death and resurrection, as summarised in the Creed/s (a collective prayer or prayers, where gathered Christians publicly affirm such faith). 

As ever, please allow for the fact that various parts of the wider Christian community may be selective as to precisely which elements in the stories they will accept and honour.