Is it possible to remove visibility of all the Tabs/Objects?

You can just remove the visibility via the object configuration by unticking this tick box - see below. 

Just note: if any of the objects are made visible via a condition, the condition will just need to be removed on the field (if it is configured this way). The way you will know this is if the object is already made 'invisible' via this tick box (as the visibility is done via the condition against the workflow):

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