knit_child in a loop - variable as title - r

Question

Following this and this stackoverflow-questions, I tried to use knit-child inside a loop, containing a variable-defined title.
Instead of the variables (e.g. A, B, C) as title, I get them with # still attached (# A, # B, # C)
Parent:
---
title: "Untitled"
output: html_document
---
```{r,include=FALSE}
library(knitr)
```
```{r,echo=FALSE}
titles<-LETTERS[1:3]
```
```{r,include=FALSE,echo=FALSE}
out = NULL
for (i in titles){
out = c(out, knit_child('Child.Rmd'))
}
```
`r paste(out, collapse='\n')`
Child:
---
title: "Untitled"
output: html_document
---
```{r,echo=FALSE,results='asis'}
cat("\n\n # ", i,"\n")
```
```{r,echo=FALSE,results='asis'}
cat("\n\n This text is about ", i,"\n")
```
Output:
While I would prefer:

Answer 1

The # character only indicates a heading in markdown if it is the first character of the line.
cat("\n\n # ", i,"\n") produces two new lines, then one space and then the #. Remove the whitespace to fix the issue:
cat("\n\n# ", i,"\n")

Answer 2

Consider using pandoc.headerinstead of Cat.
i = 1
pander::pandoc.header(i, level = 1)
> # 1
pander::pandoc.header(paste0("Subheading ", i), level = 3)
> ### Subheading 1

Answer 3

I recommend using the knit_expand function.
You create your Child.Rmd as
# {{current_title}}
This text is about {{current_title}}
Remember that `current_title` is a literal string, so
if you want use it in code then must be quoted:
<!-- Use `current_title` in chunk name to avoid duplicated labels -->
```{r {{current_title}}}
data.frame({{current_title}} = "{{current_title}}")
```
Then your main document shoud looks like this:
---
title: "Untitled"
output: html_document
---
```{r,include=FALSE}
library(knitr)
```
```{r,echo=FALSE}
titles<-LETTERS[1:3]
```
```{r,include=FALSE,echo=FALSE}
expanded_child <- lapply(
titles
,function(xx) knit_expand("Child.Rmd", current_title = xx)
)
parsed_child <- knit_child(text = unlist(expanded_child))
```
`r parsed_child`
Results: