Congrats on getting clean.
The smell and taste of black tar is something I still think about sometimes, and I haven't touched it for 13 years. Every time I smell BBQ sauce I think of heroin.
Derealization and dissociation is something that happens to me if I'm under extreme stress/anxiety. Or if I've been doing a lot of certain various drugs.
I think its very unlikely these are symptoms of drug induced brain damage, that generally manifests in other ways, and opioids generally do not cause brain damage (unless through overdose/hypoxia).
They are both normal-ish things to experience in recovery. It takes a long time to psychologically get over heroin.
Olfactory hallucinations (smells), and derealization/dissociation could potentially also be signs of something more serious, like a brain tumor, but I wouldn't worry about something like that too much. It may be worth visiting a doctor anyways if it doesn't go away or gets worse.
