Here are the changes

Surface Pro 2 updates includes: 

Surface Pro UEFI (v2.4.950.0) and Surface Pro Embedded Controller Firmware (v24.1.50.0) updates enhance system stability with microSD products, improves compatibility with Power Cover, and increases the reliability of sleep state transitions. Surface Pro UEFI update also provides support for PXE boot with the new Surface Ethernet Adapter.  Surface Pro System Aggregator Firmware (v2.4.350.0) update improves sleep state transitions when a Surface Cover is attached.  Surface Accessory Device (v2.0.287.0) update improves sleep state transitions when a Surface Cover is attached.  Surface Power Cover Firmware Update (v2.0.288.0) improves reliability when the Power Cover is attached to Surface and folded behind Surface.  HD Graphics Family (v10.18.10.3496) update improves Miracast wireless display experience and enhances display stability.

Source Microsoft Surface Pro 2 update history page Surface 2, the tablet with ARM processor got the following changes: 

Surface 2 UEFI (v4.21.500.0) update enhances overall system stability, including boot and reboot scenarios, compatibility with Surface Power Cover, and increased battery life when Surface 2 is not in use.  System Aggregator Firmware (v1.0.50500.0) update enhances the charging behavior of the Power Cover.  Surface Power Cover Firmware Update (v2.0.595.0) update improves battery life when using the Power Cover with Surface 2.  Surface Platform Power Driver (v2.0.557.0) update improves battery life when used with the Surface Power Cover.  Audio Driver Set (v 9.17.13.2819) and Display Driver Set (v 9.17.13.2818). This update provides enhanced support for external displays, improves the Miracast experience, and enhances the overall system stability while reducing power consumption in many scenarios.  Surface Accessory Device (v2.0.583.0) update enhances the experience when using a Surface Cover.

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