The symbols of the Russian army have nothing to do with fried or foe. They originate in identifying which Russian army the vehicle is supposed to belong to, mostly pre-war.
Exactly my point, the symbols are used to identify to which unit a craft belongs.
How do you fool an IFF? Give a brother a source here. If you have hacked their military codes, maybe. But even those change all the time.
We know Ukraine destroyed and captured a lot of air defense systems. It is possible that they got valid codes in such an incident and just used them before they were changed. But obviously, that is just a wild theory, however it should be possible to happen.
Plus, no friend of yours would be flying with a malfunctioning IFF responder during a war. If they did you would receive warning from command in advance. Otherwise what are the chances it's a malfunctioning friendly versus an enemy? If you're not going to shoot down aircraft failing IFF check in a war, you might as well not use IFF at all. What you're describing is a non-issue.
Again in theory you are right. But on the other hand battle damage on helicopters is quite usual, not working communication or IFF aren't surprising, but of course a reason for concern. You don't want to just kill your pilot flying back from a hard battle, you want to make sure that it really aren't your own, so you try to get confirmation.
And when you think about the proven incompetence of the Russian air defense soldiers and their general lack of quality communication it becomes plausible that they wouldn't shoot at what they must consider a damaged Russian craft flying home, as they wouldn't expect Ukrainians flying into Russia.
This might however change now if this incident makes them paranoid, but it would lead to a massive increase in friendly fire.