did the political and social structures of rome changed alot or hardly ever during the empire?

Answer 1

when Rome was a Republic starting out, she hard fairly a large amount of money but with many in poverty. As she became an Empire, the line of rich and poor was divided farther. There were many people who tried to help the poor but the rich - aka senators and emperors - wouldn't allow it, hence many were killed in trying to create equal rights.
Social structure changed from mud and brick huts to elaborate works of art and masterpieces we can see today.
At the beginning of the empire, there were many strong and capable rulers (some nice, others mean) but they could do the job.
After Constatine and the coversion to Christinanity (365?), the Empire began to fall.
Once Rome was sacked in 410, then in 455, and the last emperor, a 12 year old boy was murdered, the empire fell into the hands of the Goths and other barbarians.

Answer 2

They changed a lot. In general, the trend was from a strong emperor to a weak one; by the end of the empire, the chief generals and wealthy citizens had at least as much power as the emperor, and spent most of their times fighting one another for complete control. Socially, there were a number of changes too; the most important were related to the treatment of non-Romans within the empire.