photo stream 2 ipads

You can't view photo stream on icloud.com. You can only view a publically shared photo stream from iCloud.

What you may not realize is that photo stream photos are only held in photo stream for 30 days. After 30 days they are removed from your photo stream but will stay on any devices that have already received them. Chances are the photos you don't see on your iPad 4 are older than 30 days, so they are no longer in your photo stream but remain on your iPad 1.

You can either:

1. Save the photo stream photos on your iPad 1 to the Camera Roll (which you do in iOS 5, as I recall, by opening the photo stream album, tap the arrow button, tap the photos you want to save, then tap Save), then import them to your computer (as explained here: http://support.apple.com/kb/HT4083), put them in a folder on your computer, then sync them to your iPad 4 by connected it to iTunes, checking the folder containing the photos on the Photos tab of your iTunes sync settings, then tapping Apply at the bottom and syncing; or
2. Use an app like PhotoSync, which can wirelessly transfer photos from any album between your devices.

You're welcome.