Size

Yes you can use the Magic Keyboard if both are iPad Pro.

What you need

• An iPad Air (4th generation), iPad Pro 12.9-inch (3rd, 4th, or 5th generation), or iPad Pro 11-inch (1st, 2nd, or 3rd generation)
• iPadOS 14.5 or later

The first generation of the Magic Keyboard (A1998) is functionally compatible with the new iPad Pro 12.9-inch (5th generation) with Liquid Retina XDR display. Due to the slightly thicker dimensions of this new iPad Pro, it's possible that the Magic Keyboard may not precisely fit when closed, especially when screen protectors are applied.

No, not possible. Whilst functionally equivalent, the Apple Magic Keyboard for iPad is physically model specific.

The iPad attaches to the Magic Keyboard for iPad using an array of magnets - the positioning of which differs between the 11” and 12.9” models of iPad Pro. Similarly, the relative position of the three-contact Smart Connector differs between the 11”and 12.9”.

A further physical difference is the position of the rear camera array cutout of the Magic Keyboard. These also differ.

As such, you cannot use a Magic Keyboard for 12.9” iPad Pro with a 11” iPad Pro - or vice versa.

No, it will not work

LotusPilot is correct, the Magic keyboard is size dependable.

Only Magic Keyboard for iPad Pro 11-inch (3rd generation) and iPad Air (4th generation) can be use interchangeable.