Unable to change a pipe to be a normal file

Answer 1

How can you make the pipe a default text file, such that the first letter changes to d?

The first character of 'd' means that that entry is a directory - not a normal file.

Answer 2

Unless there is some other complication that hasn't been mentioned, the easiest is to use the big hammer:

$ rm outside
$ touch outside

If there is a process currently using the file, you will need to kill the process first, then restart it so it uses the new file. Otherwise, the pipe will stay open but invisible until the process finally dies.