Here are some Delta migration General understanding
Data Migration Tool migrates data created only by Magento's own modules (eg.
Orders, Customers Profile) and is not responsible for the code or extensions made by third-party developers.
If these extensions created data in the frontend database and the merchant wants to have this data in Magento 2, then ...
Tables starting from m2_cl are not default tables for Magento 1.9 version but they are created while using Magento data migration tool. They are basically deltalog tables.
More details can be found at this link
If you have placed orders on dev site for testing then your increment ID is updated so you need to do the migration again on Fresh Magento 2 site and then you have to merge the customer, order, and product on dev Magento 2 site.
After then create the clone of Magento dev site (clone 1) and do the testing on clone 0 sites.
if all works perfectly.
You can ...