Inquiry regarding Workflow Policies

1.) If say my workflow that I call from my workflow policy has encountered an error what would happen? Will it cause an some disturbance on other processes as well?

2.) I was planning on calling a workflow from a workflow policy but sometimes some scenario makes it run too long. will all the other workflow policy not work until my workflow policy finishes?

3.) Are there other alternative to workflow policy? I want to trigger my workflow when a status is updated to a specific value

4.) If say my workflow policy was triggered will it only run my workflow once for each time it triggered?