You must present your passport and an application for a visa to the Chinese embassy. There is lots of information online about how this process is managed.
Yes, a European citizen needs a visa to travel to the USA, unless they are eligible for the Visa Waiver Program.
Yes.
One can apply for the visa. The applicants must have clearance certificates from the police.
a USA citizen can stay in Japan for up to 90 days without a visa
Yes, an Iraqi citizen can visit the USA, but they typically need to obtain a visa before traveling.
Yes, as a US citizen, you do not need a visa to travel to Ireland for stays of up to 90 days.
Yes, a Russian citizen can travel to the USA, but they typically need to obtain a visa before entering the country.
You do not need a Visa to travel to any SADAC country, and most developing world Commonwelath countries. You do need a visa to travel to any EU country and to the USA
Yes, a Colombian citizen can travel to the USA with a valid visa or through the Visa Waiver Program.
Whether you need a visa or not depends on your nationality, not where you are travelling from. German citizens do not need a visa for the USA. If you are not a German citizen you need to ask the question again.
No, a visa is not necessary, as Japan is in the visa waiver program, but that would require an ESTA from you.
You don't need a visa if you have a biometric (electronic chip) passport and you are staying in the USA for 90 days or less for business or pleasure travel. Otherwise yes you need a visa.