#1
during auditions i will need to :articipate in call-and-response exercises. The audition team will play short rhythms and melodies, which you will either sing back or play back on your instrument. You may also be asked to identify intervals and chord qualities. The audition team will also gain a sense of your ability to match pitch during this section of the audition.

any recomendations for arists that i should learn their songs by ear with simple melodies, computer programs, or other things that will help?
#2
Well find out the melody with your ear and put it into (for example) guitar pro and try to sing the melody.

Or just start training your ear. Listen songs and learn them with your ear. It may take alot time first, but later it will be easier.
#4
easiest way to prepare for this is to start tabbing things out. if you tab out a few songs then you've already got the hang of playing things on your instrument by ear. I would recommend starting with songs based round simple guitar riffs - maybe oasis or arctic monkeys. If you can tab out the main riffs of these songs quite quickly then you're already there.
The only 6 words that can make you a better guitarist:

Learn theory
Practice better
Practice more