1. For Teams is not a "normal" Teams Room account
For Teams is an application that you install on a Windows 10 device. Once installed, this application connects to your Office 365 organization. This is the reason why the For Teams application needs to be authorized via your Office 365 tenant.
See this article for more information: Office 365 Consent For Teams Go & Talk
When the For Teams application joins one of your Microsoft Teams meetings, it is not regarded as a Teams User but as a "bot". From a Teams perspective, this bot is a guest and receives the same level of privilege. So, when For Teams joins a meeting, you should treat it as a guest, even if it's an internal meeting.
Even if you've configured your For Teams with an Exchange Room account, For Teams will not use these credentials to connect to the Teams conference. The Exchange Room Account is only used to access the list of meetings.
2. Guest and lobby management
When you schedule a Teams meeting, a lobby management policy is applied.
You can refer to this article for more information: https://support.microsoft.com/en-gb/office/change-participant-settings-for-a-teams-meeting-53261366-dbd5-45f9-aae9-a70e6354f88e
Since the For Teams application is considered as a guest (even if it is configured with an Exchange room account that belongs to your organization), you should allow "everyone" to bypass the lobby, as described below:
If you decide that only "people in my organization" can bypass the lobby, then you will have to connect to the Microsoft Teams conference (with your Microsoft Teams application) and allow the For Teams (Kickle Room) to enter the meeting.
To access the meeting options for your meetings, click "meeting options" in your Microsoft Teams meeting: