How do I make something like this in Blender? Is it possible to set a boundary for the model for certain frames then remove the boundary afterward? 
See the image, first the model is set within a smaller canvas(the laptop), then remove the boundary so model will show in entire scene. Meanwhile laptop canvas will act like a portal hiding part of the model, kinda similar to cutting a section with a plane surface in Vred.
(https://www.youtube.com/watch?v=xSlA-EREDr8
@6:45-6:53)
Sort of. You can animate a mix mask with transparency for both models and keyframe the mix factor so they appear and disappear exactly when you want them to. Alternately, you can simply make two completely different scenes and composite them.