INNO TROUBLESHOOT - Questions Here

[reiji777]

I've seen the scripts from some installer.
1st installer (tombraider survival) didn't put any registry code

[Registry]

2nd installer (sleeping dog) put one line of registry code

[Registry]
Root: HKLM; SubKey: "SOFTWARE\{code:GetAppPublisher}\{code:GetAppName} "; ValueName: UninstallString; ValueData: {uninstallexe}; ValueType: string; Flags: UninsDeleteKey;

3rd installer (mass effect 3) put many line of registry code on their scripts

[Registry]
Root: HKLM; SubKey: "SOFTWARE\BioWare\Mass Effect 3"; ValueName: Install Dir; ValueData: {app}\{code:GetMyAppExePath}; ValueType: string; Flags: UninsDeleteKey;
Root: HKLM; SubKey: "SOFTWARE\BioWare\Mass Effect 3"; ValueName: Display Name; ValueData: Mass Effect™ 3 ; ValueType: string; Flags: UninsDeleteKey;
Root: HKLM; SubKey: "SOFTWARE\BioWare\Mass Effect 3"; ValueName: GDFBinary; ValueData: {app}\Mass Effect 3\GDFBinary_en_US.dll ; ValueType: string; Flags: UninsDeleteKey;

etc..

all the script can install and uninstall perfectly.
what is the difference between three of them?
how do i recognize a game which required alot of registry code to be inserted in the script or not at all?
if I don't insert the registry key, then the game wouldn't compatible for the future updates of the game? (like in the first ver. splinter cell blacklist installer)
sorry for my bad english