How to upgrade Android 2 to 3 or 4 on GT-I9000? All is in the title. I have got a GT-I9000 (samsung galaxy S) and I do not understand why I cannot upgrade the android version ?

Why an android version is linked to a specific phone ?
First, you probably cannot update to Android 3.x as that version was only intended for tablets.

Second, no Android version is linked to a specific phone. But each phone needs specific adaptions due to different hardware elements used, so each Android version must be adapted to be usable on the device.

Third, for "How can I..." and "Where do I find..." and "When is it available...", please check the questions (and answers) already dealing with this:


How do I update the OS on my device? (includes links to "When does my device get the Android x.y update" for most Android versions)
Can every Android device be updated to the most recent Android version?
What is involved in upgrading Android to a later version, if the manufacturer no longer supports the device?
and others (check the "Related" and "Linked" sections of the questions)