Hi,
In AdWords API, you could use
CustomerSyncService.get() service, but this will not get all the changed history, this is the closest service available in AdWords API. Please check
this sample example in java. Samples in other languages can also be found
here.
CustomerSyncService only supports queries for dates within the last 90 days. In AdWords UI, you could lists the changes during the past two years and it will give you specific details to what changed. Let me know if you have further questions.
Thanks,
Milind, AdWords API Team.