Lack of experience and lack of reading any instructions are killers for any newbie being turned loose in Adobe Illustrator. Saving down to a "legacy" format is
extremely easy to do. Same goes for converting type to outlines.
Whenever I'm asked to send an Illustrator file to someone I always ask what version they're using and always convert any active fonts to outlines. If Adobe would ever bother to offer a font substitution dialog box for missing fonts in the file>open dialog I might start leaving fonts active in .AI files I send to others. Even if both users have Helvetica installed on their
computer Illustrator will default the type to Myriad if both users don't have the exact same flavor of Helvetica installed. Are they using 1950's Helvetica or 1980's Helvetica Neue? Are they using an old Postscript Type 1 version or are they using a newer OpenType build? What if they're really using Helvetica clones like Swiss 721 or Nimbus Sans? At least CorelDRAW will give users an out for this. With Illustrator you have to convert type to outlines just to be safe.
While CorelDRAW can import/export Adobe Illustrator files, its results on the import/export operations can vary greatly. Neither CorelDRAW or Adobe Illustrator knows how to properly import objects filled with interactive gradients made in the rival app. App-dependent "live" effects, such as envelopes, 3D extrusion effects and lots of other things must be "flattened" before exporting.
This is one of the big reasons why I have both CorelDRAW and Adobe Illustrator installed. I can proof the import/export results in either app and make any necessary adjustments.