Yes, the stand with the manufacturer number STN-WM55RXEN is compatible with the Samsung Flip 4 Pro WM55B. This stand is specially designed for the 55-inch version of the Samsung Flip Pro and enables a stable and flexible positioning of the display.
I suppose it should pass but it will be upright and the top of the screen tilts slightly towards the back which can cause reflections on the screen whether it's upright or horizontal. I have a 55 inch screen and frankly I was surprised at the size of the screen.
The Samsung Flip 2 65" is VESA 400x400 compatible. You can find two alternatives that may meet your needs via the following link: https://www.digitec.ch/fr/comparison/20989734-10151357
If we refer to the manufacturer's documentation, it appears that the STN-WM55RXEN is not foldable. The base with castors however seems to be able to be unscrewed quite easily.
The unit can be easily rotated at any time - no need for a screwdriver. We mostly use it in landscape format. - However, when it is connected to a PC as a touch display, you have to tell the PC to rotate it.