ooops, i did not notice that this was posted in the "scripts and plugins" section...
not sure if you can know what paragraph style is applied to a frame, but you can look for it in the developer section of the F1 scribus help.
most commands work on the current selection.
on the other side, instead of checking which paragraph style is applied, you can simply (re)apply the the style to the current selection...
does this help you?