Analysing and debuging a Typoscript for TYPO3 12.4.7

Hi, I'm looking for help with analysing and debugging a Typoscript for TYPO3 12.4.7. I have complete documentation regarding the Typoscript, though my experience with it is limited, being new to the language. I'd like to approach this project by analysing and debugging, rather than trial and error or starting from scratch. If you feel you're the right person to help me with this project, I'd be very grateful and would appreciate your assistance. I do not need a new Typoscript beeing done, I want to know why my working script form Typo3 Version 7.6.20 do not run under TYPO3 12.4.7. So what are the differences between 7.6.20 and 12.4.7 ?