I am currently a student of Games Software Development at University, about to enter my final year. During my time as a student I have been required to complete a number of assignments to do with games development, most of which have required the use of Unity.
During my first year I needed to re-create a classic PS1 game (Kurushi) using the Unity engine, and was successful in attaining a high grade (90%) for my work.
As well as using Unity as part of my University course, I have used it for my own personal use, for better understanding, I have even placed as a finalist in Sumo Digitals Rising Star Game Development Competition, in which I underwent a 2 week Games Development task using Unity to develop for the Universal Windows Platform.
I would be using BitBucket as my online Git Based Repository to backup the code, as well as keep you in the loop as to what stage I would currently be at in the project.
I would require 21 days for this project due to your requirement of the build being fully bug tested, I believe bug testing is just as important as the actual process of making the game, so I would need an appropriate amount of time to test and fix the build before finalising.
If you require any more information, feel free to contact me and ask questions.
Thank you.