Question

how did the non cooperation movement unfold

Answer 1

majatma Gandhiji had proposed that the movement should unold in stages.
It should have begun with the surrender of titles that the government awarded, and a boycott of civil services, army, police, courts and legislative schools,council and foreign goods. Then, in case the government used repression, a full civil disobedience campaign would be launched.

movement start with boycott but after some time it turn into violence in some places like chauri chaura.

Answer 2

Gandhiji had proposed that the movement should unfold in stages.
It should have begun with the surrender of titles that the government awarded, and a boycott of civil services, army, police, courts and legislative councils, schools, and foreign goods. Then, in case the government used repression, a full civil disobedience campaign would be launched.

The movement did start with boycott and swadeshi measures but it turned out to be violent in some places, especially the Chauri Chaura incident which marked the end of Non Cooperation movement.