What are the acts that invalidate the prayer?

1. Eating something less than a small chickpea in prayer does not invalidate the prayer. If more is deliberately put into the mouth, it invalidates the prayer. Putting sugar in the mouth and melting it invalidates the prayer.

2. According to the scholars of the Hanafi madhhab, a job that can be done with two hands is a work that invalidates the prayer. Doing a job three times in a row in the same ruku is also considered to do a lot of work. (For example, standing recitation is a rukn, tahiyyat is a rukn, prostration is a rukn…) Walking three steps in a row is a deed that invalidates the prayer. Two steps won't break it.