For the create PT do you need to reference that some functions (such as setScreen) are from code.org in the comments?
No. AppLab is a programming language option on the Create task, as with any programming language any procedures that are available for use in the programming language do not need to be attributed.
It would depend on the context of the situation. If you were going to publish your code on a hosting platform (e.x. GitHub, BitBucket, etc.), it would be good to specify that some of the functions are App Lab built-ins. However, if you are only planning to use the code only in App Lab, there would be no need to specify that the function is from App Lab
good point! I think the question was about the creates in particular, and with that in mind I would actually tell students to not post their create pt code in any online platform as this can lead to some plagiarism issues