The drawing you posted has 0 3D objects. FLATSHOT works on 3D objects.
What you posted was a 2D drawing with some components having a Z value. Lots of info on making those types of drawings have Z=0.
Members who use BricsCAD as their main CAD product can now add the Lite, Pro, BIM or Mechanical versions to their profile. To do so, go to your profile page, click on Edit Profile, look for My Software and select your BricsCAD product from the drop-down list at Main CAD Product.
Sounds like @steven-g will have sorted you out.
Alternately you can hold down the Ctrl button, and you should then be able to move it, even if it is locked.
If you look at the complex linetypes with letters, supplied in your posted acad.lin (Hot Water Supply and Gas Line) you will see the U factor has been added already.
Be warned that all text fonts are not the same sized characters, so when you make a text feature in a complex linetype, your x, y and s factors might need to be tweaked for different fonts.
If one opens this file (and the backup file) in a text editor programme, all one sees is a continuous word of 180 pages length. It is all the same character which is usually an invisible one that cannot be seen in Wordpad, but is seen in Word if one sets it up correctly.
So, even if the file started life as a drawing file, it is now nothing as all the data has been overwritten.
The Rectangle command is just a command that creates a 4 sided polygon using the length and width dimensions that you provide. Once the command is finished, you're left with a closed polyline. That's why, when you select the rectangle and look at its properties, it lists the object as a polyline, not a rectangle. So there are no length or width values.