Q: Running 4K and 2K daisy chained off 2015 rMBP OS X 10.11

I have a early-2015 retina MacBook Pro 13" with OS 10.11.1, the lowest end model w/ 8gb RAM, 2.7 i5, 128GB SDD, and the Iris 6100 graphics. I am currently running a 1080p Asus and a 2k Dell U2715H, each connected to their own Mini DisplayPort on the laptop.

I really like the 2k Dell and want to replace the 1080p with a Dell 4K P2715Q. But I want to free up a port on my computer and daisy chain these using MST through the DisplayPort 1.2 setting.

Before buying the new 4K display, I tried activating DP 1.2 on the 2k display. All I got was a black screen that would just enter sleep mode. So, the monitor seems to think that my computer cannot run DP 1.2 even though the laptop still showed the 2K Dell as being connected.

Am I missing something? Has Apple changed their minds, now allowing us to do more than mirror displays through a single mDP connection? I thought that is what the whole MST functionality was supposed to do, which it seems I am unable to activate.

First off: How do I activate the DP 1.2 on the monitor and have it work? It seems that OS X should automatically detect this and change the output. The display info through system settings shows that it is connected through “DisplayPort” and nothing more, nothing less.

Second, can I daisy chain a 2k and a 4k through one mini DP 1.2 even?

Third, can I test daisy chain functionality by plugging the old 1080p in to the current 2k monitor? It has an OLD DVI connection connected to a DVI to mini DisplayPort adapter; should I get the mDP to DP adapter to make that able to plug into the 2k for testing purposes?

Is there somewhere in OS X that I am supposed to adjust the settings, allowing DP 1.2 to run?

Now, the true dream would be to hook both of those displays to the AppleTV and run in full resolution wirelessly, while using the laptop from the couch... Hey, a customer can dream, right?

Thanks in advance for your help!