Food grains - branded

Dear Sir/ Madam ,

We have exempted supply of Food grains where we sell the product using other person brand NAME.

Like wise we have around 9 to 10 parties, where in that 1 party has been registered his BRAND name.

So, now what ever sale made using that registered brand party name :- 

1. should i charge tax on that registered brand sale even though food grains are exempted ???

2. whether it is deemed that i have to charge GST on sale of all other remaining brand parties because 1 person is registered his Brand name ???

3. Labour charges provided to sale of such exempted/nil rated supplies, whether RCM applicable ????

kindly clarify the above doubts, 

Thanks in advance.