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.)

You can customize those from :COSSTARSETTINGS:. You'll need to turn off the auto scaling to be able to enter a value manually for the base symbol scale. Note that this only applies to future items, not existing ones in the drawing.

Notice that you can also supply your own symbol catalog containing these symbols if you wish to customize them further,

I have experienced rare cases where a line (the wall in this case) is somehow removed when using a cutting symbol on it. If you experience that windows/doors after the first don't seem to align anymore, this may be the cause. Hit :CC2REDRAW: immediately and see if the entire thing disappears.

If it does, the best way forward is to simply use undo a couple of times, back to before you placed the symbol that broke it, and then start with a window in another location first.

If it is to late to do an undo, the easiest is usually to just use a wall from the drawing tools (right click the :DD2WALL: button to get all the wall tools) and draw a new one, unless it is a really complicated shape. To make sure it follows the existing floor, either just rely on the snap points if the room was drawn with them initially, or use the :CC2MODEPT: modifier (F5) to make the wall corners line up with the floor corners.

You need that version of the .NET framework. The major versions are intended to be installed side-by-side, not being replaced by the just having the "latest".

Windows should set that up for you automatically, just hit the install button in the error message (and restart CC3+ after the install is done.)