Is it possible to divide an annotation feature class elements in Arcgis Pro (using ArcPy) by a line or polygon into several parts?
If you mean through arcpy and not calling some tool from the geoprocessing tools, you will have to look at the available methods in the geometry you are interested in. There are "cut", "intersect", "clip" and a variety of methods for geometries.
Whether they apply to annotation feature classes is another issue, since there is no particular case for that in the arcpy tree
Polygon—ArcGIS Pro | Documentation
I tried the use of geometries and some geoprocessing tools (Erase, Clip, Split, Intersect), but none of the them work for the annotation feature class.