Can a pepper plant that is going on 3 years old (in an ample sized pot be cut back?

Question

The plant has new leaves coming out of the good sized main stem of the plant .

Answer 1

There are a few things that you need to do each year to ensure that it stays productive. You will want to cut back very hard to shape. After this, remove the pepper from the pot and cut off the bottom 1/3 of the root mass. Remove all old soil and replace it with fresh soil. Water this in, and wait! This will restore vigor to your pepper each year.

https://www.gardeningknowhow.com/edible/vegetables/pepper/how-to-grow-indoor-peppers.htm