Is Elementor Pro Required to Use OceanWP Theme and Ocean Extensions?
No, Elementor Pro is absolutely not required in order for you to be able to use OceanWP theme and/or Ocean Extensions, be it free or pro.
All Ocean demos were created using the free version of Elementor, while the Ocean Elementor Widgets pro extensions functions with both free and pro version of Elementor.
Whether or not you will actually use Elementor Pro on your website and in combination with Ocean Pro Extensions it is completely up to you.
If you decide to use Elementor Pro, both Ocean Demos (free and pro) and Ocean Elementor Widgets will function without any issues.