Applicant and assignee are not the same thing. To change the applicant you will need to file a "request to take action" from the new assignee and a new ADS. See MPEP
325 Establishing Right of Assignee To Take Action in Application Filed On or After September 16, 2012 [R-10.2019]
An assignee who is not the original applicant must become the ...
Assuming you have access to the file on PAIR, any updates should essentially be in real time. In other words, once an office action response (or other document) is filed in a publicly available case, that filling immediately becomes public.