I tried googling it but couldn't find an answer.
If I cancel my DVR subscription can I still use the app to play my previously recorded shows and skip commercials or is there a different software that I I can use to do that?
The app will stop working once your subscription ends.
The recordings are mpg files on your computer or NAS and you can move/copy/play them with any software you want.
One way would be by going to the Experimental settings area on the DVR settings page, and enabling the "EDL Export" option.
Then you could use Kodi to watch the files and it should skip commercials automatically.