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Django is rendering template from the database efficient

This is not a HOWTO question, as it, as such, has been answered before here
I am trying to integrate Django with modern frontend framework, and I found that it is possible to store and render Django templates from models. Since it is not a standard, I am wondering what are the advantages (or disadvantages if that's the case) of file based templates.
Reading though the documentation, I have seen that it is recommended to actually cache templates and models as much as possible for best performance, so why would it not be recommended to store templates in the database? It seems very convenient to me that in doing so pages can be edited from the admin panel (where you can add a code editor), which, along with the rest framework and a front end framework synergize very well.
From my research, the template tags and template language seem to work and the context can be passed in a view as well. the only thing I cannot figure out is the {include .. } tag, as it does not seem to point to a view. (although a custom tag cam be made to have this function)
Can such a setup be used in production? or are there security/performance/other concerns?

It's not recommended because templates are the developer's responsibility, not the site admin's.
Otherwise, there's not much performance difference between reading files directly from filesystem and from database.
One drawback of this approach is you don't get revision history (using git, mercurial etc). Sure, you can implement something similar to save the revisions in the database, but then why not use the better tools which already exist?
There's a Django flatpages app which lets you save HTML content in database. But the purpose of the app is to allow site admins to edit HTML content, such as information for an "About Us" page, because writing this info is not a developer's responsibility.

Django two apps frontend and backend

I am new in Django so I have a question for start working with it. Now I am writing my apps in PHP and Yii2. In Yii, I have to separate apps (frontend and backend) with two auth mechanism. But I want go to Python with Django I know that is admin site but I dont know how to clone functionality like Yii2. I need two different pages for login users (admin and normal users) and 2 panels for them.
Should I use two difference instances of admin site or write it manually?

You don't need to have two different instances. Since the admin pages (backend) are shipped with django out of the box, you can just start building the frontend. Be sure to register your sites to the admin pages for the models you are using.
I recommend going through the great django documentation:
Django Documentation
The django-admin is pretty straightforward and works great out of the box. You are somehow limited in terms of customization though. It depends on what your goals are an how much functionality your administration needs.
More infos here.

Does django have something similar to resource in rails?

I just started learning django. I was a rails developer before that. I was wondering if there is anything similar to resource in rails in django? Or do I have to make different urls and corresponding views for those urls? Thanks in advance!

django-smarter provides a similar pattern.

You are asking about RESTful APIs to the django models if I understand correctly. Django does not do it for you natively (as jpic said) but there are some packages you can install to do that:
django-smarter (as jpic said)
tastypie
django rest framework
See https://www.djangopackages.com/grids/g/rest/ for a list of APIs that can be added in to django. I see django-smarter isn't on that list. Maybe someone should add it.

customizing Django look and feel in Python

I am learning Django and got it to work with wsgi. I'm following the tutorial here:
http://docs.djangoproject.com/en/1.1/intro/tutorial01/
My question is: how can I customize the look and feel of Django? Is there a repository of templates that "look good", kind of like there are for Wordpress, that I can start from? I find the tutorial counterintuitive in that it goes immediately toward customizing the admin page of Django, rather than the main pages visible to users of the site. Is there an example of a "typical" Django site, with a decent template, that I can look at and built on/modify? The polls application is again not very representative since it's so specialized.
any references on this would be greatly appreciated. thanks.

Search for generic CSS/HTML templates, and add in the Django template language where you need it. Because unless you are trying to skin a particular app (such as the admin system), there is nothing Django-specific about any of your HTML.

The fact that you're thinking in terms of Wordpress templates, and that you think the tutorial's poll application is highly specialised, are hints that you haven't really grasped what Django is. It isn't a content management system or a blog engine, although it can be used to build those things.
There's no such thing as a typical Django site, and it simply doesn't make sense to have pre-packaged templates, because the front end could be absolutely anything at all - like a poll.
You write the template like you would write any standalone HTML+CSS page, perhaps with placeholders for the content, then turn those placeholders into actual Django template tags. If you know how to do write HTML, then you know how to make a Django template.

Actually Django does not have a "look and feel". You are probably referring to the built in Django Admin application. That app comes with its own templates.
There are third party applications that can change the Admin interface, Django Grapelli is a great example.
For any other application you want to build yourself, or download. Most likely you'll have to do the templates yourself. In order to come up with something pretty you need to learn about CSS/HTML/JS and design principles as the Django Templates will quite likely be out of your way.
I always recommend HTML Dog for learning the basics of HTML, CSS and JS.

Multiple-instance Django forum software

Does anyone know of a django forum plugin that allows each member to have his own forum? If there isn't anything, than what would be the best way to accomplish this with a "regular" forum plugin for Django?

I once created a feature matrix of all Django forum apps I could find. It might be a bit outdated now, though (contributions welcome).
At least django-threadedcomments uses generic foreign keys, so you can attach a message thread to any database object, including users.

Look at DjangoBB.

Yep, the forum app of SCT can be used for this - simply set it up and create multiple "community Groups" (these are similar to vhosts) and map them to subdomains - each community group would have separate forum categories, can have separate templates, separate user permissions, etc. (but they will obviously share the same django users and their profiles) - as an example.. the following websites are all hosted on the same instance:
SCT website
My personal website/blog (the blog is also based on SCTs forum)
ShelfShare Community

Check out diamanda. I'm not sure it does what you need as far as the each user having its forums, but that's probably not too hard to hack on top. Probably as simple as adding a few ForeignKeys into auth.User to the diamanda models. In general django pluggables and djangoapps are good places to look for django stuff that is already written. Also, check out pinax.

I believe the Sphene Community Tools can do this.