Getting error eg. unexpected keyword or identifier in htaccess file, how to remove it or is there any other way to remove file extension from url

Question

My .htaccess file code

RewriteEngine On
RewriteCond %{THE_REQUEST} /([^.]+)\.html [NC]
RewriteRule ^ /%1 [NC,L,R]
RewriteCond %{REQUEST_FILENAME}.html -f
RewriteRule ^ %{REQUEST_URI}.html [NC,L]