1) I did ask earlier why you wanted this as there may be a better option, but you have not replied to this. There are several ways to get this. Do you want it historically or instantly? You could read the job output on the spool and then extract the data you want. You could read the syslog and do likewise. Or you could use the TWS program interface to enquire on the job. This is probably the option that I would use, but any method is going to requires some post processing to get the data in to the format that you want. Running the PIF with the following command will extract details for all operations in error and this includes the error code. You can also pass it the JOBNAME parameter to limit it to the one job you are interested in.
2) One occurence will be dependent on the previous occurence if you have defined it in that way. Have you? I do not know. I don't know what you mean by a post installation process causing the JCLI error either, hopefully you are clear on this.
When you say "added an occurence of the application to the current plan" do you mean that you added one in manually using option 5.1? If so, there's your answer, you added in one occurence with a particular, specified IA time. Why do you think that there would then be any others? The run cycles of the application, whether using the EVERY option or not, are used by the daily planning process.