Do I need to install all of the 8.2 hotfixes before upgrading to Version 9?
No, you do not have to install hot fixes. The only requirement is to run upgrades for all major version, e.g.:
7 -> 8.0 -> 8.1 -> 8.2 -> 9
Make sure you load the website once after you finish the upgrade for each major version to let the storeprocedure.cs to update data.
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