1. Album created on your iPad from photos in the Camera Roll album can be deleted directly on the iPad. But that only deletes an alias to the photo stored in the Camera Roll album. To actually delete those photos you need to delete the photos from the Camera Roll album.
Photos deleted from the Camera Roll album and not immediately deleted. They are moved to the Recently Deleted album where they can reside for 30 days should you want to recover them. If you want to delete those photos permanently to free up space on the iPad then delete them again from the Recently Deleted album.
2. Photos in albums that were synced from your computer using iTunes on the computer are removed by doing another sync with the computer. Connect your iPad to the computer, select your iPad in iTunes on the computer, then deselect the unrated albums in iTunes. When you click on Sync in iTunes the albums will be removed from your iPad and they will remain on your computer.