HTTPS ReWrite + Basic Auth + IP Whitelist + FilesMatch

RewriteEngine On
RewriteBase /folder/

RewriteCond %{HTTPS} off
RewriteRule ^(.*)$ https://www.example.com/folder/$1 [R=301,L]

<FilesMatch "file.php">
<If "%{HTTPS} == 'on' && %{REMOTE_ADDR} != '1.2.3.4'">
AuthType Basic
AuthName "Password Required"
AuthUserFile /home/example/public_html/folder/.htpasswd
Require valid-user
ErrorDocument 401 "Authorisation Required"
</If>
</FilesMatch>