Question

How did the boundaries of the Roman empire change?

Answer 1

ring the reign of Augustus the boundaries of the empire were reinforced, favored in it's expansion, and created new important centers for spreading the Roman way of life.

Answer 2

The boundaries of the Roman Empire changed during the reign of Augustus the boundaries of the empire were reinforced, favored in it's expansion, and created new important centers for spreading the Roman way of life.

Answer 3

Take off everything before "during" and you have proper grammar. That's redundant.