Resolve data discrepancies between v2 and v3 of website

We recently had to completely recreate a membership website from a relatively stable v2 to a new v3. We still have v2 accessible via a subdomain (inc FTP), v3 is now live. Full access can be given to v2 and v3 backends via our hosting platform.

As a result of this re-creation, all IDs for all entries in the WP databases changed. Various scripts have been created to pull over the v2 IDs in to the v3 world so that we can re-link all the entries - e.g. users, products, memberships, orders etc. - but it has caused a lot of data issues. The site uses Wordpress, with an Elementor framework, extensive use of the Advanced Custom Fields plugin, and WooCommerce with WooCommerce Memberships addon.

There are still several main areas that need detailed investigation and resolution, and are at a relatively systemic/back end/database level rather than a front end level. Known current examples (and therefore the scope of this project):

1) 3 (relatively lightly used) user forums are not showing on the front end on v3 but were on v2. The data needs to be moved over if it hasn't been already, and made live on v3
2) VAT has been incorrectly added on v3 for imported v2 orders that contain a membership product (which is VAT exempt). This needs to be removed to clean up the headline reporting figures shown for gross income
3) Users that changed their email addresses on from say a@a.com to b@b.com on v2 have had their user profiles set up as a@a.com (rather than b@b.com) on v3. This needs to be changed. We have a list of 5 known examples, but there are thousands of users on the site so a script is required to compare and update.
4) Add the ability for admin users to search the v3 WooCommerce orders by the v2 WooCommerce order IDs if this is possible
5) Any associated front end HTML/CSS required to reflect the end user output correctly given points above