Hi, I will try to answer each one, one by one.
(A1)The minimum requirements are:
UiPath Studio along with preinstalled UiPath Robot (UiPathStudio.msi)
Orchestrator with UiPath Robot separately installed (UiPathPlatformInstaller.exe) (Manage, schedule, monitor multiple robots/environments and importantly using Queues)
UiPath Robot (Just execute existing workflows, check their logs)
(A2): Yes you can install only the Robot without the studio if you run the setup file as administrator and perform a custom setup
(A3): Yes as per (Q2) the only difference is that this installer comes along with Orchestrator, which you can choose to skip in custom installation.
(A4): Yes if you provision the Robot to the respected Orchestrator
UiPathStudio.msi is for The UiPath Community Edition
UiPathPlatformInstaller.exe is for The UiPath Enterprise RPA Platform
(A5): Yes you are. You can request the Community Edition if you are an individual or small company or the Enterprise Trial if you are an enterprise