Hi, mksr.
Thank you for visiting Apple Support Communities.
I understand you need some assistance sorting out the issue that you are experiencing with the iCloud Control Panel for Windows and your Photos. The current iCloud Control Panel available at this time for Windows 7 is 3.1. Using iCloud Control Panel for Windows 5.1 requires Windows 10.
System requirements for iCloud
If you were able to get iCloud Control Panel 3.1 installed for Windows, you will only have access to the My Photo Stream feature. This allows you a look at the last 30 days of photos on your computer or iOS device.
If you sign out of iCloud or turn off My Photo Stream on your iPhone, iPad, or iPod touch, all of the photos in the My Photo Stream album are removed from that device. Any photos from My Photo Stream that you imported to the All Photos album and the Photos tab are also removed.
The photos from My Photo Stream on your other devices aren't affected. Photos from My Photo Stream will stay on the iCloud server for 30 days from the date you upload them to My Photo Stream. If you sign in to iCloud with the same Apple ID and turn on My Photo Stream on another device, the photos will automatically download.
Before turning off My Photo Stream, you should save any photos that you'd like to keep to your device. Learn more about saving your photos.
My Photo Stream FAQ
If you upgraded to iCloud Photo Library and you want to access all of your photos, you can view them at iCloud.com and select Photos. You can also download them directly to your Computer via the outlined steps below.
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Go to Photos on iCloud.com.
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Do one of the following:
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Click Moments to see your photos or videos grouped by time and location.
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Click Albums, then click an album to view its contents.
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Click Select Photos.
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Select the photos or videos you want to download, then click Download.
The largest available version of each photo and video you select is saved in your Downloads folder on your computer (or other folder specified in your web browser’s preference or options settings).
iCloud: Use the Photos app on iCloud.com
You can also recover deleted photos by going through the steps outlined below.
You can recover photos and videos you deleted in the last 30 days.
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Go to Photos on iCloud.com.
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Click Albums, then select the Recently Deleted album to view its contents.
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Click Select Photos, then do one of the following:
In regard to your question about backing up your iPad, here is an article that outlines what data is backed up to iCloud.
iCloud: iCloud storage and backup overview
Please let me know if you have any additional questions.
Cheers