A couple scenarios for you as I am curious to view your opinions on some gray areas in recruting

:
1. If a candidate who works for one of your clients contacts you directly to inquire about a position he saw posted on your website, should you work with them?
2. If a candidate is presented to you by one of your recruiting "split partners," and that candidate works for one of your clients, should we present them opportunities?
3. Say you have on the "back burner" a client that you only present candidates to from time to time, but are never invited to really conduct searches for. Is it okay to recruit from them?
4. If I have a client who is a well respected firm in the industry, but have not placed anyone with them in over a year because they have not really given me any business, is it okay to source them?
Please let me know what your thoughts are on these scenarios.
Thank You.