- Short version:
Will it work? No. At least not in my case, no.
Can it charge MacBook? No.
- Long version:
First of all, we need to know what we can expect. 4K 60 Hz video signal requires more than 10 Gbps bandwidth, which exceeds the bandwidth of Thunderbolt 1. Therefore the maximum video quality we can achieve with A1398 is 4K 30 Hz. Well, this is not acceptable for gaming but should be enough for photo editing. Do not expect 4K 60 Hz on your (and my) MacBook.
I have both Mid 2012 15" MacBook Pro Retina (A1398) and Ultrafine 4K 24 Inch. To pair them up I recently purchased the Apple Thunderbolt 3 to Thunderbolt 2 Adapter and Apple Thunderbolt 2 Cable (2m). Sadly this setup didn't work as expected.
My MacBook can recognize the monitor, including model, resolution, color profile, and even brightness adjustment. It can also read the hard drives connected to the monitor. Unfortunately, the monitor kept dark without any reaction. Not even backlight.
My MacBook Pro can get device information from system information, Thunderbolt. It is also outputting 4K 60 Hz video signal. However the signal is somehow not recognized by Ultrafine. Sadly Ultrafine does not have any buttons or other interfaces, so I have no way to get more information from monitor side.
- Any other methods?
Since the thunderbolt method does not work on my MacBook, we can try consider connecting through USB-C with DP Alter.
We need a Mini DisplayPort to DisplayPort adapter, and a DisplayPort to USB-C adapter.
There are many USB-C to DisplayPort but very few of them work in both direction. Be careful when choosing them.
But I am not sure if this would work or not.
We may discuss more on this if you are interested.