Is it possible to change the website demo from one to another?

My question is a little vague, but let me explain.
At this point we have say demo 7. And have it modified to our taste (colors, additions, etc. etc.)
Now we have seen demo 2 and would like to implement some of the features (looks, banners, the way the homepage is set up, etc.) to our demo 7. (or.. take some of the features of demo 7 and implement that easily to demo 2). Now.. what is the easiest way to do this without disrupting a lot? I guess I can take apart the homepage of demo 7 and see what I want to keep, switch to demo 2 and put stuff back… but.. what if it messes everything up?
From what I can see, the pages are made up out of building blocks. Is there an easy way to see a homepage of demo 7 and see how that is made up, so that we can implement that to our current homepage?
(without just clicking on demo 2 and hit install and overwrite our whole site with a totally new look (which would trash some of the features we’ve added manually)

Hope it made sense.. and that you can help me here!

I could give you a hint of what I do with my site. You create a staging site on a subdomain (or a new folder inside public_html) and then install WordPress and newspaper. Then import the demo you want with the content.Then copy the shortcodes inside the homepage of the test site and create a new page on my original site and paste the shortcodes there. I then try to modify the look using td composer to match my site look. Maybe you should try it. But you should test thoroughly coz some of the elements may or may not work. (I don’t work here)

@Simion. Thanks for the tip. I have been doing it the hard way all this time. Thanks.