Problem:

I can not open up Block Editor and it throws a Javascript error in the console.

Solution:

Please clear your browser cache and try again.

Checking with another browser showed the editor.

Problem:
Conditional display based on custom field value using PHP

Solution:
You can use the Types PHP API function types_render_field() to get value of custom field.

You can find proposed solution in this case with the following reply:
https://toolset.com/forums/topic/conditional-on-php-shortcode/#post-2314245

Relevant Documentation:
- https://toolset.com/documentation/customizing-sites-using-php/functions/
- https://toolset.com/documentation/customizing-sites-using-php/