Ubuntu – How to launch the Calculator through Terminal

You can use the Compiz Window Rules plugin for this.

1. Make sure you have the CompizConfig Settings Manager installed and run it.

2. Then, enable the Window Rules plugin:

   

   and set it so that windows with the class Gnome-terminal are matched:

   

If you're using a different terminal, use the + button to build up a match expression for your terminal.

If you'd like your terminal to be fullscreen instead, you can use the appropriate rule in the plugin's config dialog.

In newer versions of Ubuntu (definitely in 16.04) you need to have compiz-plugins installed package to access Window Rules.
If you don't have it you need to install it with sudo apt install compiz-plugins and reboot.

When you perform a search on the home scope, there are a number of inputs that influence which scopes will be queried including:

1. Scopes selected through the filters (either through "Categories" of scopes, or directly as "Sources").
2. If the search term includes a keyword (e.g. your example of calculator:1+1).
3. Recommendations from the smart scope server based on the search query (e.g. if the search term looks like an equation it recommends asking the calculator scope).

It is probably the third one that is enabling the scope usually, and that recommendation doesn't come through if you've disabled online results.

I don't think there is an alternative way to force it to be used unfortunately.