Transfer Magento 2.3.3 Custom Theme and customised module files to Live site

Looking for someone to Migrate Magento 2.3.3 Custom Theme and some customised module files to Live site. I have got a new theme developed on a newly created development site.

The development site was created with a copy of the LIVE site with same third party modules. Then the developers added some new functionality within the new theme and also installed some new third party modules to the development site. They also edited some of the existing third party extensions files to work with the new theme. Everything is done on the development site and I need someone to migrate and apply all this work to the Live site.

The new theme was in development for over 6 months and even though the development site was created from an exact copy of the live site, the live site has changed a lot since then. for example all the third party modules have been updated to the latest version on the Live site whereas on the development site none of the modules were updated. so there is a difference in their version so you only need to apply the CUSTOM CHANGES of those modules and cant copy and paste the entire module directory.

Important: You need to keep a note of all third party module files that have been customised and keep a separate copy of these files with their full path in a text file. This way I can still update those modules in future and then apply these custom changes again. I need someone very experienced with this as I do not want any extended downtime during this transfer.

Apart from that, the following couple of things are needed to be done but these can all be done after the successful completion of the above task:
1. Fix a Minor Menu fold/unfold issue on initial load on mobile devices.
2. Move the position of a few blocks.

Regards