It can be used. I cannot answer the question about the additional cable because I do not know which cables are already present - the charger does not come with any cables.
I have purchased additional cables that withstand transport particularly well: https://www.digitec.ch/de/s1/product/xtorm-cx011-a-c-1m-30-usb-kabel-5889772.
Yes, that is possible. I use it for iPhone, iPad and Watch for the whole family. Charging time approx. 40 min and the iPad Pro 12.9 is at 85%. Would buy the part again, but then with more than just 2 device ports. GLTA
I have a huawei p10 that comes with a quick charger of 5V/2A to 5A. I am not sure if it's compatible with this charger, because this charger can't give more than 3A. And voltage of 9V is higher than factory charger, I am afraid the high voltage will break the battery. Any one have an idea about that and can suggest a backup charger for huawei p10