The PortalAlias table contains the list of all domains that can be used to access your website.
In order to load the application, one of these domains should match your binding in IIS (as long as auto add alias is not enabled).
Removing old records from this table is not necessary, however, you must have a valid entry for each Portal, this in order to be able to load them with your new development domain.
For example, if you have a regular Portal, you would simply need to add a new entry, such as newdomain.com. On the other hand, if you have a localized Portal, you would need to create an alias for each culture, such as newdevdomain.com/en-us and newdevdomain.com/es-es.
Finally, in case you have several Portals, that need to be accessed using the same domain, you can use newdevdomain.com/1 for PortalID 1 and newdevdomain.com/2 or another one and so on.