This question never received an answer, so, while I am no expert, I’ll give it try:
The reason why you can no longer access ligatures, ornaments, small caps etc. is because Adobe has changed its practice and no longer encodes these glyphs to the so-called PUA (Private Use Area). These glyphs do not carry a unicode value and are therefore inaccessible except through OpenType replacement rules that must be supported by the respective application.
Version 1.012 of Adobe Caslon OTF was PUA encoded
Version 2.015 of Adobe Caslon OTF is no longer PUA encoded
“People buy commercial fonts every day only to find out, that all the advertised ligatures and alternative characters cannot be accessed in their word processor or that their favourite browser cannot show the figure set they would like to use.”
In this respect, the introduction of OpenType has proven to be a step backwards for many average users. For everyday ease-of-use things were a whole lot simpler when in the PostScript-Type-1 era ligatures, ornaments and small caps were sold as separate fonts “SmallCaps/OldstyleFigures” or “ExpertSets” and could be accessed simply by changing the font in the application’s drop-down menu.
See also the related discussion here https://forums.adobe.com/message/2674677#2674677
and this enlightening article here http://typography.guru/journal/hidden-glyphs-in-your-fonts/