Registration Requirements

yes you have to apply for registration as your aggregate turniver exceedds 20lakhs (threshold limit for registartion) ( other than north-east state)
“Aggregate turnover” means the aggregate value of all taxable supplies (excluding the value of inward supplies on which tax is payable by a person on reverse charge basis), exempt supplies, exports of goods or services or both and inter-State supplies of persons having the same Permanent Account Number, to be computed on all India basis but excludes central tax, State tax, Union territory tax, integrated tax and cess

and
Interest received from a local bank is payment for an exempt supply of financial service 

But "Giving loan or deposit is supply of service. It is exempt only if the consideration is by way of interest"

and exempt supply is to be considered while calculating aggregate turnover

Notification No. 12/2017- Central Tax (Rate) (Heading 9971) exempts interest from GST. 
And Order No. 01/2017-Central Tax states specifially:  "in computing his (person opting for composition) aggregate turnover in order to determine his eligibility for composition scheme, value of supply of any exempt services including services by way of extending deposits, loans or advances in so far as the consideration is represented by way of interest or discount, shall not be taken into account"
i.e. it is excluded from calculating agg turnover of compo scheme dealer only.
 

GST not applicable on Salary and Interest....

GST applicable for Commission amount and Required Registration for Commission business....