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None of these is the correct way to run a backup.

The first try is closest to what you probably have to do but there needs to be a space after php. Remember that /usr/local/bin/php is the command (it executes PHP CLI) and /home/acianf/public_html/cli/akeeba-backup.php is the argument (the PHP file to execute with /usr/local/bin/php, in this case the backup script).

If you cannot get it to work you will need to ask your hosting company for help. They will know what is the correct path to the PHP CLI for 7.4.32 and the path to the files in your site's cli directory.

Side note: You say that you're hosted with Amazon Web Services. Based on the path I suppose that you are using Amazon Lightsail which comes with support which is why I told you to contact your host. If you were using a self-hosted Amazon EC2 instance you'd be on the hook for figuring out how to set up CRON jobs on your own environment since using EC2 means that you are your own host and responsible for your environment. This doesn't look the case, unless you're using a prepackaged server such as a Bitnami instance, in which case you have to indeed figure it out yourself.

Either way, we cannot know how you server is set up and what the paths to the PHP executable and your site are. I can give you an idea of how wildly these can vary depending on server setup. On one server, managed by a commercial host and using cPanel with EasyPHP, the path to PHP 7.4 CLI is /usr/local/bin/ea-php74 and the path to my site's cli directory is something like /home/ahjwxpk/public_html/cli. On another server, self-managed with Ubuntu Server 20.04 and PHP installed through the Ondrej PPA, the path to PHP 7.4 CLI is /usr/bin/php7.4 and the path to my site's cli folder is something like  /var/www/mysite/cli. My local server running on macOS 13 with packages installed via HomeBrew these paths are, respectively, /opt/homebrew/Cellar/[email protected]/7.4.30_1/bin/php and something like /Users/myuser/Sites/mysite/cli. All of these servers run the same version of Apache and the same version of Joomla. Yet they are so drastically divergent inter setup I couldn't tell you these paths in any way but for the fact that I set up two of these myself and the third one, the commercial host, I asked my host to tell me.