Any Twitch Questions?

So I started with Twitch and I have a few questions about it and hope someone can answer that ^^

1. The imprint as an affiliate - is it mandatory?

2. What do I have to observe legally in a merch shop (of course my own designs, logos, etc.)?

3. Does a logo have to be patented? If so, what are the costs?

4. Can I stream YouTube videos or react to them? If so, what should be considered? Can the stream be recorded in the Videos channel? Which videos can be used?

5. The donations must be included in the tax return. Is that correct?

6. Does a small business have to be registered as soon as income is generated?

Yes. For scope see § 5 TMG.
what do you mean?
No
whose videos should be streamed? Of course, you need the consent of everyone who can be seen in the video.
You can't accept donations because you are not a non-profit organization. You can only get commercial income, no matter what you call it. And yes, they must appear on the income-excess-account for the tax return.
You have to register the trade as soon as you put your offers on (§ 14 GewO). You can't register a small business because it does not exist.

Thank you very much! Yes, if you have to observe something legally, register, do something with the product beforehand, register don't know ^^

And videos such as B. Funny moments or something.