Prestashop Upgrade & Compatibility

I need my store moved from Prestashop 1.7.8.10 to the latest stable release without losing a single feature, order, or customer record. The shop runs several custom modules and also contains a few direct core tweaks that must be kept intact, so the upgrade has to be handled with care.

Here’s what I’m looking for:
• Back up the full site and database, then set up a staging clone.
• Perform the version jump to the newest Prestashop build.
• Audit each custom module, update or patch it as required, and prove it works under the new version.
• Re-apply or refactor my existing core modifications so behaviour remains identical.
• Verify that catalogue, checkout, payment, shipping and back-office functions operate normally.
• After my sign-off on staging, schedule and execute the live switch with minimal downtime and a clean rollback plan.

Please be comfortable with Prestashop upgrade best practices, module debugging, and database migrations. Share a brief outline of your intended approach and a realistic timeframe; I’ll supply module lists and server access once we agree.