Coding for custom form issue

I’ve been using Wix for some time now and want to be able to do some more complex coding for the site, to create content such as flash cards and specialized forms. So I hired a programmer to test out one of my page ideas, after learning of the new API possibilities. However, he told me that for the form he was working on “I looked on the entire api documentation to see if it was possible to add/change attributes so I could implement the above tasks [wordcount, prevent copy/paste and disable the spellchecker] but Wix only allow certain attributes to be changed and that’s not enough.”

This was in December of 2017. Was he correct, and if so, has this changed since then?
Thanks for your help.