Excluding workflows

[Skeferstat]

Hello,
I am new, so please forgive me for asking the following questions:

1. Once my workflow is canceled I don't want to start it again. But when starting the next workflow, this one (the "broken") is continued first. How can I exclude a workflow from processing?

2. Where can I see what the status 0, 1,2, etc.... mean?

3. What is the greylist and what is it for? Who can fill it?

Thanks!