Hello, 
I am not sure what you are requested to do. 
In general, if value of code part is used on transaction, it cannot be deleted. 

And I would be reluctant to delete project from IFS/Project module - there is a lot of system connections relating to project. 
Perhaps the best option if project is wrong for some reason is just to create another project, with correct information, and then transfer required data to the new one (e.g. repost actual costs to new project using manual voucher).

I appreciate the information and advice you have shared.