Can a grocery store formed under partnership or LLP open a online commodity trading a/c too?

1. yes.

2. Grocery business Income from business and profession
MCX Commodities profit loss - Income from business profession

YES CERTAINLY.
PROFÌTS WILL BE TAXED AS PER THE FOLLWING
1. NATURE OF ASSESSE
2 COST OF ACCQUSITION
3. FAIR MARKET VALUE.
4. WHERE INDEXED COST OF ACCQUISTION IS APPLICABLE THEN APPLY THAT.
5. COMPUTE CAPUTAL GAINS
6. COMPUTE TAX ON CAPITAL GAINS
7. INDIVIDUAL AS PER SEC 112A ITS 10% IN EXCESS OF RS.1 LAC
8. SHORT CAPITAL GAIN 15%
9. PRIOR TO 2018 IT WAS LONG TERM CAPITAL GAIN AND EXEMPTED FROM TAX UNDER SEC 10(38).