Yes, on Snapchat, you can choose to allow friends to contribute to your story. It's a fun feature that promotes more interaction among friends. You just need to adjust the settings accordingly.
You can use certain apps that offer the option to take screenshots without triggering notifications. But be careful, it might violate Snapchat's terms of use.
Sorry, there's no way to view Snapchat stories if you aren't friends with the person. This is a security feature of the app to ensure users have control over who sees their content.