Openshift: Jenkins in a separate project
You can do that by adding Role-Based Access Controls, granting the Jenkins service account access to the project.
oc policy add-role-to-user edit system:serviceaccount:cicd:jenkins -n <project_name>If you need more help the free e-book "DevOps with OpenShift" is a good one. It covers the requested details in Chapter 4.
Of course, it's recommended to have a CI/CD project with Jenkins and a separate one with your app.Tutorial: https://youtu.be/tUqwKQsHLkY