"when a report or analysis was created" : If you have enabled usage tracking then use saw_path, and min(START_TS) to find out when it was first time ran and you can treat this as created date (if you have renamed /re-saved as different name then you may not see accurate data).

" list of agents that run successfully during a time period"   : From agent backend tables you will be able to see this information. Use following query , tweak the query as per your need.

select

COUNT(T688819.JOB_ID )

from

     BI_BIPLATFORM.S_NQ_JOB_PARAM T688823,

     BI_BIPLATFORM.S_NQ_JOB T688819 ,

     BI_BIPLATFORM.S_NQ_ERR_MSG T688820,

     BI_BIPLATFORM.S_NQ_INSTANCE T688822

where   T688819.JOB_ID = T688822.JOB_ID and T688819.JOB_ID = T688823.JOB_ID and T688820.INSTANCE_ID = T688822.INSTANCE_ID and case  when T688822.STATUS = 0 then 'Completed' when T688822.STATUS = 1 then 'Running' when T688822.STATUS = 2 then 'Failed' when T688822.STATUS = 3 then 'Cancelled' when T688822.STATUS = 4 then 'Timed Out' when T688822.STATUS = 5 then 'Timed Out' else 'Something Else' end  = 'Completed' and  TRUNC(T688819.LAST_RUNTIME_TS) = TO_DATE('2017-08-09' , 'YYYY-MM-DD')

and case  when T688823.RELATIVE_ORDER = 1 then T688823.JOB_PARAM end  is not null