Transitioning from r76 to r85

Hello, I would like to update my web application from three.js revision 76 to newest (r86) , but I can't figure out pipelines on how to do it properly. The main problem I'm facing, is that after a year of progress and updates three.js team made to their library, new functionality arrives with altered coding workflows, rebuilt objects etc. My question is: are there any easy ways (replace files) to update my web application with new version of three.js (or at least get its new funcionality) without rewriting thousands of lines of code in my app? Or do I have to just update my code according to a new standard? I understand that updating about a year worth of three.js progress is not an easy task, I just want to consult with the pros.

Thank you for your help! :)

P. S. I a'm asking this question because workflows like OBJMTL importing has changed. And I am struggling to addapt my code according to a new standard.