There are hundreds of languages in India, some similar, others completely different. If by g you mean jee, as people will often refer to Gandhi as Gandhijee, then I think's a term of affection and respect....
Yeah that's right. Hindi, Urdu, Bengali, Goan.......and there's many more although Hindi and English are the two languages that piece together all the states that make what India is today.
If you mean 'ghee', it is a type of clarified butter one might use in Indian cuisine. I think it is a Sanskrit word; one of the many, many languages spoken there.
Ahh, G's just the initial of his name. Like Ali G. It's a DJ thing to do. Desi means local/indiginous and is used to refer to South Asians. So I'm assuming DJ Desi and Sandhu G are two disk jockeys....