How to Save All notifications?
Settings > Notifications > Messages > Show in Notification Centre > … you can set up to 10 recent items

then all you need to do is swipe your screen from the top down &amp; there they are [though if you've never used that before you'll probably need to clear a whole lot of other stuff first time &amp; trim which apps actually need to be in there.]

You can't have all - only the last 10.