A) There's no hard ceiling for projects' quota, but any quota increase has to be requested on . Regularly, you may get from 5-10 projects to 50 or more, but if you need even more, then it will depend upon your usage of the service and other considerations to grant your organization an higher quota. There's a FAQ that would help you have a better idea about this .
B) Currently, immediate deletion of projects is not supported, but you may check and vote a related feature request on . According to the documentation , the project will count towards your quota usage until actual deletion of the project.
But, your quota may be automatically adjusted over time. If you deleted the project and tried to create new project and got quota limit error, but then you were able to create a new project, you may check if you can create another one, if you do then your quota may has been automatically increased. In some cases, you can check your remaining quota when creating a project .