Url Paramerters and Repeating groups not displaying correctly

Hi guys I have what seems to be a complicated set up. Maybe there is an easier way to achieve this. I will include the link to the app at the bottom. And some screenshots.

I am doing the airdev bootcamp, exercise two. So I have chosen a dummy app for a music search platform users can search for any music via artist name, Artist Genre, or song tags, they will be able to Sort the list of results by:

  • Created date (newest to oldest)
  • Created date (oldest to newest)
  • Number of votes (highest to lowest)
  • Number of votes (lowest to highest)

At the moment I am trying to set up the search function for “song tags”

DataBase set up
Artist
Comment
User

Fields:
Artist–
Album name: text
Artist Genre Tags: List of (OS) Artist Genres
Artist name: text
Artist’s description: text
Artwork: Image
Song: List of files
Song Tags: List of (OS) Song Tags
Song title: text
Views: Number
Votes: List of Users
all standard fields

Comment–
Artist: Artist
Body: text
Standard fields

User–
Avatar: image
Name: text
Standard Fields

Option sets:
(OS) Artist Genre
(OS) Song Tag

Page INDEX:
Popup Variables (hiddend from users) - used to store URL variables (see screenshots)


Group Tabs:
Each tab references the URL parameter Tabs, to show the relvant group Hidden on page load
All artists shows : All Artists in the DB
Genre shows: all Artist Genres
Song shows: all Song Tags
Contributions shows: all Artists that have been uploaded but the current user.

Group Artist Genres: (*hidden on page load shown with url parameter tag - working as it should)
All genre tabs displaying in RG a list of genres from option set,

User Clicks the desired genre (Group Artist Genres is collapsed and hidden), Group Expanded Artist Genres (not yet built) is shown with the Genre referencing the clicked genre and a list of all artists linked with that genre

Group Song Tags: (*hidden on page load shown with url parameter tag - working as it should)

All song tags displaying in RG a list of song tags from option set,
Click the desired genre (Group Artist Genres is collapsed and hidden), Group Expanded Artist Genres is shown with the Genre referencing the clicked genre and a list of all artists linked with that genre


I cant get the data source to correctly reference the selected song tag and display dynamically. I am also trying to get this group to be hidden on page load and be shown when the url parameter “expand” is true.
I want the “Expand song tag text” element to reference the “group song tag” tag;s display. and when the Url parameter in Var-expand is the same as the display in “expand song tags text” display then the group is shown.

But I cant get it to work as I wan it to. Either the “group Expanded song tags” shows all the time or not at all and the element “Expand song tags text” is always empty.

Here is the link to the app.

Any help will be greatly appreciated but Please I ask you not to just change it so it works and then let me know, I need to understand what and how it is done and why.

Regards
Simon