TDS formalities and TRC - NRI turkey

A SAAS based private company in India providing software solution on rent basis to industries along with follow ups and online software training. 

For a service it is required to take help of a company in Turkey on recurring basis and then further provide here.

My question is for the payment to this Turkey Vendor.

1. What are the formalities we have to do ?

2. What are the TDS related details that should be asked from turkey based co. ?

3. What will be the exact rate of TDS deduction?

4. Is the TRC mandatory? Kindly provide the flow chart for TDS rate if TRC is provided and if TRC is not provided.

Thanks.