Hi,
Many organizations maintain more than one environment for the implementation of a given solution. These are often defined as:
a. Test/Development - a sandbox type of environment where new functionality can be tested, apps built and rebuilt, prototyping and the like
b. Staging - This is where user acceptance and load testing is performed.
c. Production - this is the 'Live' site that's 'officially' used by clients. Prod is not to be touched prior to extensive testing.
See:
https://softwareengineering.stackexchange.com/questions/117945/staging-environment-vs-production-env...
Some (well, many) organizations don't have the resources for more than one environment, but this also presents implementation risks. It's a lot less stressful to break a DEV environment than it is to break the PROD environment.
With regard to this question:
I wanna all the computers connected to my Intranet to be able to connect to the Server/Portal and create Apps with Admin role and use the WAB Dev edition, I am afraid that you mean that ONLY the computer on which we installed these stuff, is the only one where we can do everything we want ?
This is not the case. Users of ArcGIS Enterprise won't be confined to using just this one machine, they'll be able to connect to it using a browser via the intranet.
However, because the machine you're thinking of deploying the Enterprise GIS on is a bit underpowered, the performance these user experience will likely be less than desired - depending on how many users are working with it.
If you elect to work with a multi-machine deployment, the performance impact will be lessened because you're distributing the components of ArcGIS Enterprise across two or more resources, which will lessen the resource impact on each machine.
If you're RAM constrained but can spin up multiple machines, I'd highly recommend this route rather than a single underpowered machine.
To summarize:
It is POSSIBLE to deploy ArcGIS Enterprise on a single machine that has only 10GB memory. However, it is STRONGLY RECOMMENDED - especially under an environment under any kind of production load where users are expecting the system to be available and performant - to have a MINIMUM of 16 GB RAM.