RE: How to migrate data from one Dataverse evironment to another with GUIDs?
There is a tool within the XRMTOOLBOX collection that I've used on many occasions, "Data Transporter", it is quick and easy to use, simply connect to the source and target instances and you will be shown a list of tables from source.
In it's most basic use you just select the table and hit the transfer button, it has options to Create, Update and Delete records in the target table it uses the GUID as the primary reference for matching. If you only want to transfer specific records then you can provide a FetchXML filter, I use Advanced Find to build my query, then export the FetchXML and copy/paste the filter section into Data Transporter. You can also choose to not transfer specific columns if you are having dependency issues.
You need to understand your data hierarchy so that you are transferring data in the correct sequence, e.g. Accounts, then Contacts, then other related tables.
I use it mainly for moving reference/configuration data from DEV to UAT and PROD to ensure my reference tables are all using the same GUIDS, useful if referencing specific records in processes / Business Rules.
It has recently had a new feature added called "Playlists", I've not had a need to use this yet, but it looks like it allows you to create a list of transfers to execute in sequence and then be able re-use again in the future.
www.xrmtoolbox.com/.../