I think you can, as long as the app and the pc can be linked, i.e. Chrome browser syncs your history, bookmarks, etc from phone to pc automatically as long as you are signed in. However there are lots of apps (probably most of 'em) that have been specifically developed for phone use only, which sucks
That really depends on the development behind the apps. Like i said some have sync functionality some don't. i.e dropbox, whatever pic u take on your cellphone gets uploaded to the cloud, and you can access those pics from the pc via web or the program itself (which you have to download). What specifically is that you are trying to accomplish , if u don't mind me asking?