For the redirection you should be able to use the browser built-in plugin and its "Go to url" action.
You can concatenate strings and global variables.
Ex: "..../GameSummary?UniqueID=" & UniqueIDValue & "&score=" & Score
Where UniqueIDValue and Score are both global variables.
There's no "official" way to get the value of an hidden field in the page (but you could use a third-part plugin to retrieve it and store it in the UniqueIDValue global variable).
You could also use the Browser's plugin action "QueryParam" and/or "QueryString" to retrieve values directly from the URL.
I hope this helps.