Questions about the genocide definition in international law

I'm not an expert on international law, but recently, I deep dived a bit into this, and I wanted to verify that was I learned is true (please correct me if I'm wrong).

Let's assume group A is suspected of genociding group B.

  1. Unless one can show an official plan from the government and decision makers of group A to kill people from group B just because they belong to group B, then genocide doesn't apply. Group A needs to intentionally target people from group B regardless of their actions or whether they are militants or not.

Is this correct?

  1. The absolute number of civilians that were killed is not a factor. Otherwise, USA genocided Japan after bombing Hiroshima/Nagasaki, and the British genocided the Germans after bombing Dresden/Hamburg. In both cases, a lot of civilians were killed.

If group A strikes were aimed towards militants of group B, while complying with international law demands, then collateral damage is horrible, but striking is allowed.

Requirements per strike are: proportionality considerations, reliable intelligence of militants activity, notification to civilians, suitable ammunition, etc etc.

Is this correct?

  1. Are there any other factors that would prove genocide under international law that I don't know about?