Few doubts about customizing Illdy

Hi,
I have installed wordpress locally, and am trying to develop a website using the free version of Illdy.
My questions are these:

  1. Will the ‘Additional CSS’ section get erased during a theme update ?
  2. If I add html tags to my content in the ‘About’ section, would that get erased during theme update ? (For example, I need to use header tags, img tags, newline tags, etc) Should I be doing this using css ?
  3. Which all are the files I need to import to create a child theme ?
  4. I want to install a new font, and use that for headings, etc. How do I go about this ?

Thanks a lot for your help!