Yes, of course Russia has drones. And Ukraine's air defence is depleted. Russia can hit basically whatever they want.

Ukraine has absolutely been launching terror strikes on Russia (including the territories in dispute). The stated purpose is to make the Russian people feel the pain of the war, so they aren't even really trying to hide it. It seems to be some misguided attempt to try to galvanise the public against the war, or to convince the west that they're winning somehow. The western propaganda rags have been cheering these attacks on as victory, so it's likely the latter.

Russia, needless to say, is more than a little upset about persistent attacks on civilians. So in order to retaliate, they've began attacking targets that they've previously refrained from. They've shut down Ukraine's ports, they've systematically destroyed gas stations, bridges, railways and locomotives, and infrastructure in general. And they've also been hitting more targets in urban areas.

Ukraine is hiding military sites in residential areas. This is a war crime (using civilians as shields). There's been a few high profile incidents recently where ammo dumps have been hit in residential areas. Ukraine was even embarrassed enough about it to scapegoat a few people.

Western media reports strikes on such facilities as attacks on civilians. But the truth that I see is that Russia is sick of Ukraine's blatant war crimes, and they seem interested in shutting down Ukraine's MIC and critical infrastructure in response, even if the targets are in residential areas. This is going to be a hardship for civilians, and is likely the reason Russia refrained from doing so before. But I would argue that this is going to save lives on both sides. Russia has absolutely no reason to target civilians deliberately. They're clearly trying to be seen as liberators, and attacking civilians does not win wars and is counter to that stated purpose.