No.3 is freebase, No.4 is HCl. Where I come from (Pacific coast) all the dope was formerly sold as 40%-60% caffeine and the remainder heroin HCl, which people would smoke, sniff, or inject equally well.
Nowadays though, the fentanyl trade has fucked the heroin game five ways to Sunday. A recent study that surveyed some 200+ opioid users in the downtown core of Vancouver found that not a single one of them was free of fentanyl - evey single urine sample they collected had fentanyl or metabolites thereof. Even the people who insisted "my guy gets uncut heroin".
My reckoning for what happened is that fentanyl started to get mixed into crappy cut dope to make it sell, then pretty soon it was mixed into good dope to give it that "kick". Sooner or later there was no market for uncut heroin because people's tolerances were jacked through the roof. Fentanyl went from being added at 0.5%, to 1%, to 5%, to 10%, to 20%... people started keeling over in the streets, the dope game became like the crack game, addicts who formerly could last a day without down turned into fiends who needed $20 every 2 or 3 hours or they'd be incapacitated.... and then came carfentanyl, which not only was even More potent, but also lasted longer than fentanyl. More overdoses. Now there's all these addicts who are hooked on chemical weapons. At least they can go half a day without robbing someone now.
There is no better time to get the fuck off opioids if you are in my hood. I feel sorry for the poor bastards who panhandle and scrounge through dumpsters to support their habit. Between the coronavirus and the crappy dope game, life must be unbearable. Glad I'm not on the streets any more.