Does the official Upgrade Service cover compatibility of custom and third-party modules?

[ECUADORDMAIN SA]

Hello,

We are running WHMCS 8.13.5 in production. We want to update in two steps:

1. Stay on the 8.13 branch and apply the maintenance updates in order: first 8.13.6, then 8.13.7.
2. After that update is complete and verified, move to WHMCS 9.1.

If we purchase the official WHMCS Upgrade Service, does that service include checking compatibility of our existing custom development and third-party modules for both steps, or does it only update WHMCS core?

Please confirm:

1. Whether the service can apply 8.13.6 and 8.13.7 first, and 9.1 afterwards, or whether it only upgrades straight to 9.1.
2. Whether custom hooks, custom order-form themes, and local addons are reviewed as part of the service for both versions.
3. Whether third-party registrar and payment gateway modules are included in that compatibility check.
4. What happens if something custom is not compatible with 8.13.7 or with 9.1.
5. What you need from us to confirm this before we contract the service.

Thank you.

[sentq]

Based on the official WHMCS Upgrade Service description, the standard service primarily focuses on upgrading WHMCS itself, applying template updates to one custom theme, and preserving existing customizations where possible.

However, it does not explicitly include a comprehensive compatibility review of custom hooks, order forms, custom developed addons, or 3rd-party modules. Nor does it guarantee that incompatible customizations will be updated or fixed.

Your requirements go beyond a standard WHMCS upgrade, particularly since you're planning a staged upgrade with compatibility verification at each step.

For a production environment with existing custom development, I would recommend working with an experienced WHMCS developer