hello, I had my female sim get this career from city hall, then I see guitar icon on career panel.

1. Is only guitar allowed to earn money from this career or other instruments from Late Night are allowed too?
2. Is it available to make money from only 'playing for tips' or includes jamming too?

Thanks for home schooling mod. It's so annoying to go to school everyday in Isla Paradiso. LOL.

Yes, you can earn money from playing all instruments not just the guitar. I don't think you can make money from jamming, but once your instrument skills are high enough, level 5 I think, you can make money from tips and you can make a lot of money playing for tips in the subway. Just click on the subway station and "play for tips". See this guide, scroll down to Playing for Tips. Hope that helps.