Gst on sale of ice-cream & other restaurant items (need clarification on high priority)

Dear Experts

I am Raghava- CA Final student.The following are the Grievances that need to be addressed

1. We have a Client who is engaged in Ice-Cream processing business , he gets raw material from foreign country and he sell ice-creams along with other restaurant items- whether he need to charge Gst 18% or 5% need Clarification along with example?

2. The same client took Master Franchisee from Foreign company, that he use himself and also sell franchisee to other parties for the certain years by charging consideration- My doubt is that - will it be covered under same line of business that i mentioned above & need clarifications on tax implications?

3. And also the same person is involving in Outdoor Catering Services- will it be a same line of business & I need clarification on tax implications?

 For all Services is it enough to have 1 Gst Registration or will it be considered as a Vertical line of Business-Guide me?

Thanks in Advance

Raghava.