For Self-hosted clients, As the service hosted at the client-side, so we just need to deploy our newer version at the client's server. Rest, you just have to add new fields as mentioned in the Migration Document at your end as per your requirements.
The best part, you can test our newer version. and your current version will also run as it is. Once you will approve that you have successfully moved to the newer version, then we will disable the older version from your side.
If you still have any questions, you can always contact RChilli Support via creating a ticket at RChilli Helpdesk or simply by sending an email at firstname.lastname@example.org. The support team assists you further on this and for deployment as well.