1. Powerful engines.
2. Stage(s) integration (needs to be tested - did you notice we never tested any thing above stage one?).
3. Different kind of guidance system. (completely different. LRG/Stellar - very very very few countries have been able to master it)
4. Orbital insertion -> warhead separation -> oribital-reinsertion (physics / design / metallurgy etc etc)
6. Flight computers (flight + terminal) > No you cant stick an intel in it.
5. Telemetry.
Sorry to bust your bubble yara, it's not like throwing something into suborbital/orbital space and then wishing it would fall on your enemy (Iran). Or putting a compass in it and wishing it would recognize continents (N.Korea/Iran).
Btw, I have just mentioned the layman's version of what is required. If you get into even one critical part of it, it will take years upon years to explain it to you. It's tough. Unimaginably tough. However, I know the guys who are on it, they have done it before!