Hi:
6 dot uncontracted is grade 1, contracted is what we in Canada call grade 2. I've never heard the term UEB, so I can't help you with that. Eight-dot Braille is often called "computer Braille", and probably isn't what you want.
Your best bet for specific help with an iPad is probably the website
$1. I don't own a Braille display myself, so I've never used Braille on my iPhone.