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Akeeba Backup does not have a limit on database or site size. We've seen databases over 5GB and sites with sizes exceeding 100GB being backed up successfully.

I suspect that the warning (not error) you saw told you that some rows of your database tables are bigger than 1MB and you need to make sure that MySQL is configured correctly to handle them if – AND ONLY IF – you see the database restoration fail with one of the error codes stated in the warning message. We display that message because there is no way to ask MySQL for this value without having administrative privileges on MySQL itself, something impossible on commercial hosting for obvious reasons. So we show that message before the database restoration so of the restoration fails with one of the error codes we state in the error message you know what to ask your host to fix.

THIS IS ALL IRRELEVANT TO YOUR ISSUE. IT'S A RED HERRING. FORGET ABOUT THIS WARNING MESSAGE. Since your database restoration finished successfully there is nothing for you to do there.

So, back to your real issue.

I suspect that the error message you received and don't remember had to do about renaming files. If you have a file named htaccess.bak but NOT a file named .htaccess you will need to copy the htaccess.bak file into .htaccess  This is normally done at the Clean Up step of Kickstart unless you have a file ownership / permissions issue which is what I suspect was the message about. It also told you to do that and delete the installation folder from your site.

Speaking of which, do check that the installation folder is no longer present on your site. If it is, please use the hosting control panel's file manager to delete it.

Try to load your site. Does it work?

If not, do check your configuration.php file. Is it named exactly configuration.php (case matters)? Do the contents look like the ones you were told to put manually into it? Most importantly, does your database connection information match the information your host provides to connect to your database?

After checking that try to load your site. Does it work?

If not, you should edit your configuration.php file and change

public $session_handler = 'native';

to

public $session_handler = 'database';

This would work around your host not having a writeable PHP session folder which is what Joomla is complaining about.