Questions before creating a telegram mini-app

Greetings. I am going to launch a Telegram mini-app game with monetization.

Before I hire a team and pay for their work, I want to get independent and detailed answers to the following questions:

• Let's assume that the designer has already done their work and the developer has written the code. How should I act to ensure that access to the application and its modifications is only available to me (the founder), and in the future, former designers/developers cannot change anything? Should they send me the files, and should I personally upload them to the server? Please describe this process in detail, starting from renting the server to the file upload process, etc. Additionally, how is the functionality of the game/application checked? Should there be a test server (and is it easy to set up) where I can manually reset all progress or, conversely, "draw" the necessary characteristics ("stats") for testing?
• A question about monetization. I am considering the possibility of purchasing in-game items for "stars" of Telegram. Is it possible to create a parallel option to purchase other items for TON? Furthermore, is it possible to create a multi-level referral system where a person receives a % in TON from what their referral or the referral's referral spends, etc.? What potential pitfalls might there be?
• Continuing the question about monetization – at what stage and how should I register a legal entity to obtain this monetization? How and under what conditions do payments occur? In this answer, I would like to see links to documentation. I assume it makes sense to register a company offshore, but at a much later stage; I need comments on this.
• In-game marketplace. What problems might arise from creating an in-game marketplace for internal currency (which cannot be withdrawn yet) and for TON, which will be immediately available for deposit and withdrawal?

A report with answers to these questions is required; additional important information is welcome and will be paid for.