SO if Russia starts lobbing around chemical and biological weapons, then Ukraine should do that too? Like not gonna work like that, for example biological weapons are one of those were you can't just go "tit-for-tat". Since every biological weapon used is new risk of launching a pandemic on the world and so on.

To certain level, yes if other side breakes the rules, we get to break them also. However there is a line. Line which you never cross. Under no circumstances should Ukraine be allowed to target medical facilities, even on Russia having done it multitude of times. Indiscriminate intentional bombardment of still habited cities with no allowing of civilians to evacuate should always be off the table. You just don't do that. All it leads is to needless human suffering.

It's one thing to aim for military or strategic target and miss and hit civilians. That is recognized as reality of war. Terror bombardment? Never to be allowed. Not to mention it doesn't work. Every example in history has shown all it does is make the receiving end angry, instead of demoralizing them. It sets a "So it's to the last breath then? That is the name of the game, fine that is the name of the game" and they fight to bitter end.