Concurrent rate limit to send 429 http status by using a property

[#1]

In the apigee documentation, i see we can set a property features.isHTTPStatusTooManyRequestEnabled to send 429 status instead of 503 error when the concurrent rate limit is reached.

http://docs.apigee.com/api-services/content/comparing-quota-spike-arrest-and-concurrent-rate-limit-p...

1. How to set the property ?

2. Is this applicable for all versions of apigee ?

3. Is this per organization ? Does 429 status applicable only for concurrent rate limit proxy?

Or 429 will be sent irrespective of concurrent rate limit and for other use cases as well ?