Regarding Windows 8(.1)/Windows Phone 8(.1) lock screen apps

I was wondering about this for a long time yet I can't seem to find any answer to my question, so I'll ask it here:

If an app is not added to the lock screen, does it mean that they can't run in the background periodically and grab notifications while the screen is locked? I was wondering about this since iOS does not have restrictions like only allowing 5 or 7 apps to be displayed (and hence, run) on the lock screen, and I can let as many apps as I want to show notifications while the device is locked. Allowing only a small amount of apps to run above lock is, in my opinion, very restrictive as I have many apps that need to get info while my PC is locked (e.g. alarms, Facebook, Twitter, Skype, a clock tile, a Feedly client, Flipboard, a Bing lock screen changer, calendar, mail, weather) and I can only choose 7 of them on my PC. As to why I lock my PC, well, part of the reason is to prevent my friends from playing the fool with my social network accounts while I'm away.

Answers are most appreciated. Thanks guys :)