In the stock clipboard, only the last thing gets saved. Save something else and it overwrites the last thing. (How much RAM do you think they should allocate for the clipboard - the phone has only 1.5GB, and the more that's allocated for the clipboard, the less is left for apps to run in. You can't have an infinitely-large clipboard.)
The clipboard in a phone is exactly the same as the clipboard in a desktop - except for
some Samsung phones that allow you to keep more than 1 thing in it. (If yours doesn't, install
Clipper - Clipboard Manager - it does.)