Shamim's Plugins

Yes possible. Please follow https://www.shamimsplugins.com/support/topic/restrict-which-rolls-show-up-on-front-end-for-announcement/#post-25048

Yes, your code is not returning anything if user do not have manage_options capability. Use like following

add_filter( 'fep_menu_buttons', 'fep_cus_fep_menu_buttons', 99 );

function fep_cus_fep_menu_buttons( $menu )
{
  if( ! current_user_can('manage_options') ){
    unset( $menu['new_announcement'] );
  }
  return $menu;
}

By default “New Announcement” button is visible only to admins. No code require.
Let me know if this is not the case for you.

This can easily be done.

Please follow following.

1+2. Add following code in Front End PM PRO > Settings > Appearance > Custom CSS . This will hide both welcome section and menu.

#fep-header, #fep-menu {
	display: none;
}

3. Go to Front End PM PRO > Settings > Recipient > Max recipients and set to 0 (zero). This will hide “To” section.
4. Go to Front End PM PRO > Settings > Recipient > Can send to group and checked. This will enable group message option.

Let me know if you find any difficulty.

What permission you have set to the file? Which file permission you have changed?

It is written there that permission denied, that means there is permission issue for that file.

Please follow https://www.shamimsplugins.com/docs/front-end-pm-pro/troubleshoot/email-notification-not-receiving/

Let me know.

Disabling plugins only for testing if there any conflict with other plugins. That is not the solution but debug the issue.

I found a potential issue with that theme. That login popup is added way too late. You can add following code in your child theme’s functions.php

add_action( 'wp_footer', 'anr_wp_footer', 9999 );