Hi @ArindamM4019 just wondering if you have made any progress with this? We have come up against the same limitation in creating an offline mobile app - doesn't appear to be a way of getting conditional display logic from DX API...
If you mean the visibility of a component of a section you need to use ONLY when rules and not expression, because the latter one are not supported from DX API.
When you're talking of "cascade dropdown" what are you referring? If you mean the results list to show in a dropdown you can use the normal ways for populate the list (Data page, Clipboard). Otherwise can you explain what do you mean?
Have a nice day,
Conditional visibility : Use when rules instead of expressions
Cascading dropdowns : Use on click section refresh and pass parameter of current property value to next dropdown. This will trigger the refresh Dx API and fulfill your requirement. Too many refresh is not a good design we need to keep in mind .