Can you update a ipad IOS 9.3.5?

No.

The 2011 iPad 2 is 11-years old and has NOT been supported for many years and is obsolete.

You can reycle this device with a nearest Apple Store location or recycle the device with a local electronics recycling service.

Sorry.

Not unless it's subject to the GPS issue which 9.3.6 patches, and then only to it.

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