Footer Modifications

I would like to make the following two changes to my footer:

– Currently, the developer of my theme and the link to his website is only mentioned in the footer of the front page. I would like to display it on every page.

– I would also like to include the text “This page was last modified on YYYY-MM-DD” aligned to the left and on the same line as the default footer. Instead of YYYY-MM-DD it should obviously display the date when the page was last modified. For that purpose, you probably have to use the function “get_lastpostmodified” mentioned here https://www.ads-software.com/support/topic/adding-last-modified-datetime-to-footer. But I have no clue how to acutally do this.

As far as I know, all the said changes have to be made within the following part of my function.php

// footer link
add_action('wp_footer', 'footer_link');

function footer_link() {
if ( is_front_page() && !is_paged()) {
	$anchorthemeowner='<a href="https://codiumextend.code-2-reduction.fr/" title="code reduction" target="blank">code reduction</a>';
  	$textfooter = __('Proudly powered by <a href="https://www.www.ads-software.com">WordPress</a> and designed by ', 'codium_extend' );
  	$content = '<div id="footerlink"><div class="alignright"><p>' .$textfooter. $anchorthemeowner.'</p></div><div class="clear"></div></div></div>';
  	echo $content;
} else {
	$textfooter = __('Proudly powered by <a href="https://www.www.ads-software.com">WordPress</a>', 'codium_extend' );
  	$content = '<div id="footerlink"><div class="alignright"><p>' .$textfooter.'</p></div><div class="clear"></div></div></div>';
  	echo $content;
}
}

I have already tried to do the modifications by myself, but it always ended up breaking my whole site, and it had to restore a backup of the php file. So, any help would be highly appreciated.

– David
https://en.daevu.ch/