PARENT formula output format matches the data format used in the formula as argument. For example, if you are expecting an output as Region List in the line item, the format of the line item in which you are using the PARENT formula should be Region List. So if you are looking for Country parent then you can use ITEM formula as argument to get Region list output.
Re: Level 2 Model builder Sprint 1- SYS05 Region Details module:
@sguptatalkingrain Unfortunately as per training guidelines and rules, no one is suppose be providing solutions on training queries.
Having said that, I would suggest, you make sure you follow the training material and videos. Also name your modules, line items, actions as suggested in training material. This would help you in completing the training.