What should be SM's take on below situation

Is there little to no risk of the requirements changing during the development?

Is there any unknown complexity that needs to be considered?

A traditional waterfall approach may be fine to limit the overhead that comes with incremental development and inspecting and adapting. 

As a SM / Agile Consultant, should I suggest them to follow Agile approach? or is it good to go with Traditional Waterfall approach (as they have the final 100% requirements which are less likely to change)

@SUMIT AGRAWAL, The answer to that question would depend on whether the client wants to inspect the Increment frequently, control risk, control cost or if they would prefer to inspect everything all at once towards the end. It also depends on whether the work falls under the complex domain and requires empirical process control.

Remember, "Customer collaboration over contract negotiation."

If we go with Agile Approach then copy-paste of each Requirement in the form of Stories into Jira won't be a Rework?

If you have all the requirements and it is clear, do we really need user stories? What was the purpose and intention behind the concept of user stories?

Remember, "Working software over Comprehensive Documentation"

In light of receiving a large BRD document likely filled with a lot of unnecessary and low-value scope, perhaps a helpful initial question to them might be "What would you like to see actually delivered in the first few weeks?"