Note: I am not a visa agent and I am most especially not your visa agent.
Posting just to point you to the official sources:
Will my EOI be rejected because I am not present in the chosen state?
Can't find anything that addresses this directly. Try reading https://immi.homeaffairs.gov.au/visas/getting-a-visa/visa-listing/skilled-nominated-190#Eligibility ...
Those are indeed different categories, with slightly different rights and requirements:
Salarié détaché/ICT only applies to people transferring internally within the same company/group. I don't see any immediate advantage for you as employee but it's useful for employers as they can use it to relocate people who wouldn't otherwise qualify (i.e. lower salary ...
No, you generally cannot apply for Change of Status if you are already out of status. In rare cases where USCIS might give an exception for good cause to file late, but your case does not seem like a case that would qualify.
The requirement is that the passport needs to be valid until 6 months after the date of departure (or, for passports from countries in the 6-month club, the passport needs to be valid until the date of departure). The actual effect of this requirement is that:
If your passport is not from a country in the 6-month club, your passport must be valid for at ...
You can apply for the German freelance visa from another country.
If you want to apply from Germany, and you are not from Australia, Israel, Japan, Canada, South Korea, New Zealand, or the United States, then yes, you will need a job seeker visa.
Source: How to apply for the German freelance visa