Embed Rmarkdown with Rmarkdown, without knitr evaluation

I do this using the cat function, which works for both HTML and PDF output.

---
title: "RMarkdown teaching demo"
author: "whoever"
---

# Major heading

Here's some text in your R Markdown document. Here's a code chunk:

```{r, echo=FALSE, comment=""}
cat(c("```{r, eval=FALSE}",
      "head(mtcars)",
      "```"), 
    sep='\n')
```

Now we're back into regular Markdown in our embedded document.

Here's inline code that I don't want executed either: 

```{r, echo=FALSE, comment=""}
cat("The mean of mpg is `r mean(mtcars$mpg)`.")
```

Not sure about the pdf output, but surrounding your demo rmarkdown with:

<pre>
...
</pre>

seems to work for html.

Here is one way to achieve it. You may add `r ''` before the chunk header so that the code chunk is not recognized, and use knitr::inline_expr() to generate `r `.

````
---
title: "RMarkdown teaching demo"
author: "whoever"
---

# Major heading

Here's some text in your RMarkdown document. Here's a code chunk:

`r ''````{r, eval=FALSE}
head(mtcars)
```

Now we're back into regular markdown in our embedded document.

Here's inline code that I don't want executed either; 
e.g. mean of mpg is `r knitr::inline_expr('mean(mtcars$mpg)')`.

````

It will be easier if you just save the R Markdown example document in a separate file, and include it in the top-level document via readLines(), e.g.

````
`r paste(readLines('example.Rmd'), collapse = '\n')`
````

To include three backticks in a fenced code block, you need more than three backticks. That is why I'm using four here.