Updating Geant4 application to latest release

I have a Geatn4 application that builds under Geant4 version 10.02.p03 - I am using it under the latest release of Ubuntu, but I have also built it in Unix and Windows 10. I have in the past attempted to update the application to work on more recent releases. I had to make significant changes to the program structure, but I was able to compile and build the program and run it with no apparent errors. Unfortunately, the output from the program was quite different to what it was initially (lack of any obvious bugs made it hard to track down the source of the difference) and then I ran out of time to work any more on it.
Now I have some more time available - but before I try again, I would like to ask some advice.
(a) Previously my intention was to compile and build it for the next release after 10.02 (i.e.10.03) and then for 10.04 and so on until I go to the latest release. Is this the recommended approach ?
(b) Previously I examined the structure of the example programs built using the release
I was building against. I tried to understand the new structure this way and modify my program accordingly. Is this how others undertake this task or are there some guidance notes ? I was unable to find anything like this in the Release notes.

© Is there any further advice that can be given for this task ?

Many thanks