@rajeev2189 ... but since:You already tried the big jump and failed You are also using some customized stuff
I'd suggest going version by version until you hit something that breaks. Then examine breaking changes logs and such for that version.
Edit: Hmmm... Rereading your OP:
...challenges while upgrading.
Maybe I misinterpreted this and you have not actually already tried to update? 🤔
In which case, if not, follow pitaj's recipe above.