Do I have to upgrade to Ionic V6?

Hi all

Before I bore you with the technicalities, let me tell you what I am looking to achieve:
I am looking to make some updates on y existing app but apparently it can not happen due to the below.

My app has been developed on Ionic CLI 3.2

I want to now make a few changes and when I run source code via ionic serve, I am getting too many errors. It is asking me to update ionic CLI to Version 6. The system is also not allowing me to install an older version of the node as the node version was 5.x when I first developed this app and right now that seems to be old. If I try to use a newer version of the node then the app throws so many errors with the most common error being ‘app-script’ and many others.

Apologise if this question has been asked before but I have looked through many forums with no easy solution.

When the app was built the system was configured as below

Node - 5.8.0
Ionic Framework - 3
Ionic CLI - 3.2.0

Ideally what I am looking to do is update the app with the latest framework along with updating the other npm packages which also need updating with the latest SDK (as I heard apple will soon be requiring their members to update this in June).

Now I am trying to achieve all the latest versions but with the current app. Most probably the npm packages. If we use the latest npm then all its packages get updated that will cause to update their syntax and other things related to this, for example, FCM to perform a push notification.

The issue is my developer has informed me that do update this it will take 20-25 working days, which amounts to a conisderable cash outlay for something which is updating things. Normally when there are updates one would like to see that it is for their beneift and the cash outlay to update would be far less then then benefits. Here it does not seem to be the case.

So going back to y purpose:

1- Is there a way to avoid the full changes and still make changes to the source code and get it approved for the changes i want in the app?
If yes, can you please shed some light into this
2- If No, what is the easiest, most efficient way to overcome the above hurdles?
I would like to believe that Ioinc would not make changes to their platform as such that their existing users have to spend thousands to upgrade. This was not a cost I had budgeted for at all and due to the updates apparently I can not make changes to my app.

Any help would be much appreciated