sometimes yes, sometimes no. In both US iraq wars, the US had way fewer casualties than Iraq. Invading is harder than defending, but a country won't invade unless they think they are likely to succeed with acceptable losses.

It depends.

In this particular case Russia doesn't seem to care care about lives and uses WW1 style of waves of meat, which of course drastically increases losses

This is the most recorded war in history and I know someone(History Legends)offering a good amount if you can show him videos of these Russian meat wave attacks .