How can I download iOS 16.5 on my iPad mini?

Very simply, you can only update an iPad to the most recent version of iOS/iPadOS that is supported by the device. Interim updates are not available.

All System Updates are digitally signed by Apple - and can only be installed whilst the digital signatures remain valid. After release of a new iOS/iPadOS version, the immediately preceding version continues to be digitally signed by Apple - however, usually within a few days, Apple will revoke the digital certificate with which the earlier version is signed. 

System Software Updates are cumulative - and include all preceding feature and security updates.

Whether or not you are able to update your iPad to a newer version of iOS/iPadOS will be dictated by the iPad model - and the currently installed version of iOS. You can find this information here:

Settings > General > About

Not sure which iPad you have? Identify your iPad model.

Here is a list of the current highest version of iOS supported by the older models of iPad (for simplicity - “generations” are shortened to a number) that are restricted in their ability to be updated:

32-bit devices (obsolete)

iPad1 - iOS 5.1.1

iPad2, iPad3 and iPad mini1 - iOS 9.3.5 (WiFi Only models), iOS 9.3.6 (WiFi & Cellular)

iPad4 - iOS 10.3.3 (WiFi Only), iOS 10.3.4 (WiFi & Cellular)

64-bit devices

iPad Air1*, iPad mini2 and iPad mini3* - iOS 12.5.7

iPad Air2, iPad mini4 - iPadOS 15.8.2

iPad5, iPad Pro (9.7"/12.9" first generation) - iPadOS 16.7.8

(*) obsolete

Newer models are all able to be updated to the current version - iPadOS 17.5.1

• iPad Pro 13" (M4)
• iPad Pro 12.9" (2nd generation and later)
• iPad Pro 11" (1st generation and later + M4)
• iPad Pro 10.5"
• iPad Air (3rd generation and later + M2)
• iPad (6th generation and later)
• iPad mini (5th generation and later)

the only ios version you can install on a device is the newest signed ios version for the model of ios device you own

so you can't

Salsaman1 wrote:

I cannot upload pictures into iCloud. The sinc button will not turn off. I purchased more storage space but I cannot upload and eliminate my original pictures. Thank you.

I don't think you understand how iCloud Photos works.

It's a synchronization service. Turning it on is not supposed to completely "eliminate" photos from your device. Your photos will take up room both in device storage and in iCloud. Deleting them from any device associated with the same iCloud Photo Library will delete them from all devices connected to that library and from iCloud.

That said, you can turn on "Optimize {iPhone/iPad} Storage" on your device. This gives the device permission to keep smaller, lower-quality versions of photos in device storage, when device storage starts running low. You still need enough room in iCloud for all of the full-size originals. And you must let the system do the management - if you go and start manually deleting photos to make room, you'll be deleting them everywhere.