Update PWA Installation Popup on Wordpress

My Wordpress site has code in the footer to show a popup to install a PWA.

I need to update the code (on staging site) so that the following occurs:
1. Move PWA code from footer.php to child theme functions file
2. Ensure PWA installation popup DOES NOT show automatically
3. Show PWA installation popup ONLY when existing footer menu link “SSP Mobile App” is clicked
4. Ensure successful installation to mobile when popup install button is clicked
5. Apply same fix to live site

- I expect fast professional service and good communication
- I expect first time correct error free work
- No upfront payments - milestone/s will be released upon successful completion of project