Enable internet only for specific apps I will need to spend few weeks with no internet, but I will still have my mobile hot spot. So I wonder if I can prohibit all apps including OS (which I know will try silently to update something) from using internet except terminal, as I still want to be able to connect to my remote server and code. 

A free (and/or native) solution would be preferred but I would settle with something I have to pay for if necessary.
I think the app called Little Snitch is right for the job.

In it you can set up who has access to Internet resources, including all not so obvious background "blood suckers", like the one checking for software updates and so on.