You hookup the UI then you can change the texture used for the Image UI element for specific players.
You should be able to edit the XML directly in the UI editor. Otherwise save the map as a SC2Component folder and use Notepad++ or something similar.
2. If you Right click the list of layouts you should just be able to select Add layout and name it. The rest can be done using Notepad++.
3. You can show/hide specific dialogs for specific players. The console UI will be tricky but with the resource panel you just hook it up and then you can use the Set Dialog Item Image trigger action for specific players. The console panel models are automatically set based on the import file path https://sc2mapster.gamepedia.com/UI/Referencing gives some clues as to how to do it. You can also create a .txt file called Assets under the GameData folder of a SC2Component folder and use that to reroute textures for different races (eg. UI/ConsoleModelCommandPanel_Terr=Assets\UI\Console\Terran\ConsoleTerran\ConsoleTerran_02.m3). You can then link specific UIs to dummy races and set them based on the selected faction. Whole screen cutscenes could also work.
4.1. seems the default image is not being removed which indicates the individual buttons are not being hooked up correctly.
4.2. The buttons shown in the command panel are set based on the command card of the caster unit added to the group. The number and positioning is determined by the UI layout.
4.3. Again set by the anchors of the UI layout.
4.4. They did show up as can be seen by the hotkey letters just the image is not being shown. Again this indicates the hide animation for the EmptyImages of the UI layout are not working correctly. The lower Stukov buttons are showing because they are using unmodified command panel buttons.