Hi, I will try to answer your questions here
1) As the certification page explains ("https://education.oracle.com/products/trackp_457 ") that exam is the only step, meaning that you do not need to take additional exams or courses:
More advances certifications (like Database Administration Certified Professional) may require more than 1 step, like I show below:
2) There are 3 "levels" in Oracle Certification, usually connected one to the other, each of them meaning a higher level of knowledge (but not all paths have the 3 levels):
Associate (OCA) --> Professional (OCP) --> Master (OCM)
There are also some Expert (OCE) or Specialist (OCS) certifications that can be taken for some particular products that do not have an entire "path", they are usually like specialization paths that sometimes require at least a previous OCA or OCP on a more "generic" topic (for example, there used to be a "Database Performance" OCE that required a "Database Admnistration" OCP as pre-requisite).
Besides the levels, there are "paths" associated to products or tasks. For example, for the "Oracle Database" product there is a path for Database Administration (OCA --> OCP --> OCM) and another path for Database Development (OCA --> OCP), as there are paths for Java development (OCS) or Oracle Linux Administration (OCA --> OCP).
So, in your case, you are interested on Oracle Database, but not on the Administration path but more on the Database Development one, that is explained here:
Hope this helps!
Also, if you have a couple of minutes, please change your display name to something meaningful rather than a number, making simpler for everyone to followup a conversation: