Yes, according to Cooler Master the following accessories are included: 450 mm Extension Cable x 4, 600 mm Extension Cable x 1 https://www.coolermaster.com/catalog/coolers/rgb-accessories/rgb-led-controller/#specifications

This is an RGB controller for 4 RGB strips with 4 pin connection.

Yes, 12V. See also manufacturer's page (in the lower third under Specifications): http://www.coolermaster.com/cooling/cooling-rgb-accessories/rgb-led-controller/

Normally, you have all the information on the coolermaster website

It is necessary for the effects. This article is only compatible with the Cooler Master brand.

Yes exactly, this controller only supplies power to all LEDs. For the fans, Y-cables could be a cheap solution: Phanteks Y-cable for 4-pin PWM fan (11cm)

With every fan who supports the CM controller. Unfortunately, there are hardly any, because every manufacturer wants to sell its own controller.

Halt nicht mit dem Funktionaitätsumfang: Cooler Master Wired RGB Controller C10L Es gibt aber auch sets, z.Bsp.: https://eu.coolermaster.com/de/cooling/case-fan/masterfan-pro-120-rgb-ab-3pack-with-controller/