You cannot use the commands like that. SELBYP doesn't return entities that can be stored in a variable, all it does is change the selection mode to be by prior instead of the normal selection procedure. Also note that GE doesn't actually store an entity, it stores a set of coordinates where the entity is located, that can be used to grab the entity but it doesn't store the entity itself.

Likewise, RANDOM doesn't have a return value. The command is used very similar to the GV and similar command, i.e. RANDOM varname will cause a random number between 0 and 1 to be stored in varname. You can then manipulate this further.

The SHADEPOLY command also need a second argument for the pitch.

Also be careful with those semi-colons. Commands in CC3+ are executed by using either a new line OR a semicolon. Using both means you are basically creating an empty line, and in CC3+ that means repeat the previous command.

You can find the correct syntax of all the commands in the table in the tome, or in the spreadsheet in @documentation\tome\commands.xlsx

If you know the name of the fill to change to, the quickest is to use the CHANGEFS command. Type in the command (followed by enter), pick the poly when CC3+ asks for selection, hit D for Do it, and when it asks for the new fill, type in solid white 20 and hit enter. Changing it via the command line do require that you spell the new fill 100% correct though.

Of course, you can also use the more common GUI dialog through :CC2MCHANGE:. If you wish the correct fill style to be pre-filled in this dialog, first use the KEEP (:CC2KEEP:) command on another entity that has the correct fill, and when you then use change properties on the entity you want to change, the fill style you extracted from the other entity is already pre-filled, all you have to do is to check the check box in front to apply it.

I am guessing that when you talk about your house, you're talking about that floorplan of yours, right, and not a city-scale house symbol?

The issue with rotating a floorplan is the way CC3+ shows the outlines. When you rotate vector entities (like your floor and walls), only the outline of the entities are shown for performance reasons. But the downside is that when you have two entites on top of each other, their outlines cancel each other out. And with floorplans, you almost always have that case, because you have the floor entity and the walls entity which are in the exact same positions.

There is no other tool that can be used, but one workaround is to use the :CC2LINE: tool (or :CC2BOX: or similar) to draw a simple guide line somewhere close to the feature you want to align, and when you rotate your floorplan, make sure to include this line when you rotate. You should find that this single line will be nice and visible in the rotation preview. You can then delete the line when you are done.

I am not sure how images would work. The lines for the original lines are just plain simple lines. The easiest way to deal with them is to open up the symbol catalog for editing (@Symbols\Cosmographer\basesym.FSC), the from symbol manager, clone the symbols, and finally, go in and edit the two clones, using change properties on the lines to change their width. You can then save the symbol catalog with both your new modified copies and the original in them, and you should be able to easily pick from the starmap options which of the two to use.

(I normally don't recommend overwriting the original symbol catalog, but for this case, it may be the simplest, providing you do clone the symbols and don't change the originals. But if you prefer to be safe, either save your modifications under a new name, or make a backup of the original first.)

Node editing as Jim explains is a good option. Another good option is to use combine path to merge the walls back into one entity again. Combine path is explained in this article (you'll want to skip steps 7 and 8, as those are for turning it into a polygon, which you don't need)