Android 7, Firefox OS and Tizen in MultiROM Manager on Nexus 5

Question

Here is my question about problem with Plasma Mobile. As you can see I have updated Nexus 5 and prepared MultiROM setup without problem. Until now I found and do:

1. Android 6.01 (Internal - updated in Android settings)
2. Firefox OS v0.4 (20140603) installed from this thread
3. Salfish OS installed from this wiki
4. [IN PROGRESS] Plasma Mobile install (problem in separate question)

I see in Salfish settings that there are no updates.
I know that Google will not reloase Android 7 for Nexus 5.
I know that Firefox OS had last update in last year (2.6.0)

With all this in mind I have the following questions:

1. Is it possible to install Andorid 7 as an external ROM in MultiROM OS (from zip file)?
2. Is there any updates for Firefox OS image for Nexus 5 (zip file)?
   Note: I have a problem with Firefox OS. I can't load any web page and Firefox Marketplace, but I think it's because of not updated certificates list.
3. Is there any Tizen image (zip file) for Nexus 5?
   Note: Of course I searched before asking, but found only install tutorial for Nexus 7.

Can you link to (newer) images (zip files for MultiROM) and/or tutorials with them?

Update:
I do some search (XDA-Developers forums):

1. I think Tizen work only Samsung devices, but I'm not sure if build it is possible on other phones.
2. I found FirefoxOS from June 2016 and have too old certyficates problem. I can access sites with http protocol without problem (unless them allows to https). In new wersion (pre-release 2.6.0) I don't have Firefox Marketplace (no icon in launcher - maybe it's hidden somewhere ...) and can't change language in settings (empty list).
3. I found Android 7, but it's problematic with MultiROM setup.

Answer 1

Android 7 won't get a official rom from google u need to get a ported version or instal Cyanogenmod. FireOS is discontinued by mozilla. and tizel is samsung only. You can try Pac-Man rom.