Yes, you can just include mentioned files.

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thank you for help, I'll do hidden-* classes by my self, now I got another question, I have mdb pro version, and now I have to publish project to my customer's server, I can include mdb.min.css/mdb.min.js right?  no need to encrypt these files? or something else? thank you and forgive my poor English.  

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The hidden-* classes have been removed from bootstrap v4-beta and has been replaced by d-none classes.

* Made display utilities responsive (e.g., .d-none and d-{sm,md,lg,xl}-none).
* Dropped the bulk of .hidden-* utilities for new display utilities.
  For example, instead of .hidden-sm-up, use .d-sm-none.

To replace hidden-md-down, you would instead use both classes d-none and d-md-flex  (or block, inline, etc)
This should hide everything above size xs then display everything above size md

 

See display utilities:
https://getbootstrap.com/docs/4.0/utilities/display/

See migration notes:
https://getbootstrap.com/docs/4.0/migration/

 

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Hi, as I understand, your aim is to hide nav-links on small devices? If yes, read the documentation: https://mdbootstrap.com/layout/bootstrap-navigation/ and https://mdbootstrap.com/javascript/sidenav/, pick your example and use the right code, that's all you need, without any additional classes. If your problem is associated only with .hidden-*-down, read the documentation: https://v4-alpha.getbootstrap.com/layout/responsive-utilities/ and try, for example, use this class with simple paragraph text to see that it works well.  

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