WordPress folder and .htaccess and index.php : Load site with domain name only

Hello

I have just been working on setting up a domain on Hostgator with WordPress.
My WordPress is installed at mydomain.com/wp. The site loaded when I type mydomain.com/wp, but not when I type mydomain.com.

The WordPress files were moved by a technical person to root directory, so the site loads when I type mydomain.com.

However, I would prefer to keep WordPress in the wp folder as it was installed, as I may install other stuff and I want to keep things tidy.

I know that this is possible.

My short question is;
1. which files exactly should I move back to the wp folder, which ones belong to wordpress (not to my hosting service)
2. where should the .htaccess file be? In root or in the wp folder?
3. Which code should be in the .htaccess folder? I have come across the three examples below from a Worpress thread, from the hosting service help, etc.

Thanks for the help!

DirectoryIndex home.html index.php index.shtml page1.php

or this code

# BEGIN WordPress

RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]

# END WordPress

or this code

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress