Continuing the discussion from Introduce yourself!:
Welcome to the SketchUp Help Forum and thanks for introducing yourself.
We try to keep our forum tidy by encouraging visitors to post in the right place.
Your introduction goes on to describe some modeling difficulties you’d like to address.
Let’s discuss them here in this new topic and not add unnecessary clutter the ‘Introduce Yourself’ thread.
We’re here to help. Whenever you have a new question always feel free to start a new topic.
It also helps to introduce us to what you work with.
At times it’s hard to offer advice unless we know if you use a Mac or a PC and if you use SU Pro or Make?
You’re looking for a command that does not exist in SketchUp.
Learn the fundamentals of model organization before you invest any more time in the model.
In SketchUp, selected geometry is isolated and protected by making it a Group or Component.
Layers in SketchUp are merely a visibility attribute assigned to Groups and Components.
Visible or not, SU Layers do not to protect geometry from interaction and inadvertent alteration.
Let’s iron out the layer issues here first and then start a new topic about house models and terrain.
The following resources will get you started.
I encourage you to visit the Knowledge Center as well.
Required reading before you use SketchUp Layers…
Does SketchUp Support Layers? — SketchUp Help