Yes, photos imported into an iPad do get shared through Photo Stream. This feature is mentioned in this Apple KB article.
The 1000 picture limit is a per hour limit. Apple says (in the same KB article) that…
If you exceed one of these limits, your uploads to Photo Stream will be paused temporarily and you may see a notification message on your device. Your uploads will resume automatically once you no longer exceed one of the limits (such as the following hour or day).
In addition to the 1000 picture limit, there are further limits…
- Uploads to My Photo Stream per day: 10,000 photos
- Uploads to My Photo Stream per month: 25,000 photos
These limits can not be circumvented (as far as I know) by having your computer constantly sync to Photo Stream.
This Apple KB article explains Photo Stream resolutions:
On your Mac or PC, your photos are downloaded and stored in full resolution. On your iPhone, iPad, iPod touch, and Apple TV, your Photo Stream photos are delivered in a device-optimized resolution that speeds downloads and saves storage space. While actual dimensions will vary, an optimized version of a photo taken by a standard point-and-shoot camera will have a 2048 x 1536 pixel resolution when pushed to your devices. Panoramic photos can be up to 5400 pixels wide.
According to the same Apple KB article as the previous, yes, Wi-Fi is required for Photo Stream to work (emphasis not mine).
On an iOS device, new photos you take will be automatically uploaded to your photo stream when you leave the Camera app and are connected to Wi-Fi. Note: My Photo Stream does not push photos over cellular connections.
Prior to a recent change, Apple's solution for this would be to ensure that iPhoto was running and you have configured iCloud to automatically import all photos into your library.
Now that there is no limit to the number of photos, you just need to remain under the current upload limits to avoid having photos that are only on your device and not backed up to Photo Stream:
- 25,000 photos per month
- 10,000 photos per day
- 1,000 photos per hour
Other than temporary pauses, you should be able to store as many photos in the cloud as your have bandwidth and time to upload.
Best Answer
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"Disable & Delete" deletes only the photos and videos on iCloud. However, you would lose the originals of your photos and videos if "Optimize iPad Storage" were selected instead of "Download and Keep Originals" in your iPad's “Settings > [Your Name] > iCloud > Photos” settings prior to your selecting "Disable & Delete".
In addition, if your iPad has had little free storage left recently and "Optimize iPad Storage" were selected instead of "Download and Keep Originals", then you might also have lost some of the photos and videos you have been accessing the least in addition to originals of all your photos and videos. The number of photos and videos you might have lost in such a scenario (in addition to all of the originals of all photos and videos) would depend on how little free storage your iPad has had (if that were the case) recently.
In summary, if “Download and Keep Originals” were selected in your iPad's “Settings > [Your Name] > iCloud > Photos” settings prior to your selecting “Disable & Delete” (and you have had no trouble with the storage space on your iPad recently), you should not have lost anything at all. However, if “Optimize iPad Storage” were selected prior to “Disable & Delete”, it depends. This relatively recent article explains “What Happens When You Disable and Delete Photos from iCloud” in more detail.