Chaos Space Marines Weapons

When you'll try to compare Codexes of Space Marines and Chaos Space Marines you will notice that their weapons list is different. But why is it so? They're almost similar armies. Here is the knowledge of different weapon types I know/heard/read about.

Assault Cannon
Assault Cannon is powerful Space Marines, and Chaos have nothing similar. First I thought that it was created after Heresy, and Chaos Marines can't be equipped with those weapons because of this. But then one of Horus Heresy novels about Dark Angels mentioned Assault Cannon on Dreadnought.
It is said that Assault Cannon is not stable weapon and jams from time to time. And in 10.000 years Chaos Marines lost all of their Assault Cannons, using more stable older pattern Autocannons instead.

Autocannon
Autocannon exists in both Codexes, but it looks like only Predators and Dreadnoughts can use it. So, if weapon mentioned in both Codexes - it's obviously pre-heresy weapon. But then Chaos have Autocannon pattern for troops. Looks like this pattern was implemented just before Heresy, and Horus ordered to supply his legions first, then Mars was salvaged and loyal Marines got nothing.

Storm bolter
It's twice as effective as simple bolter, and Loyal Marines have it. It's obvious that it's pattern was found after Heresy, because otherwise Horus' elite terminators would be equipped with those things.

Demolisher Cannon
Vindicators are powered by those huge and extremely powerful cannons. But it's strange that in Codex Space Marines 2004 and Codex Chaos Space Marines 2007 they're the same, but Codex Space Marines 2008 added "Barrage" to them. Why is that? I have no answer. Maybe Matthew Ward thought it is time to modify Demolisher according to 5th edition of Rulebook and made first step like this?...

Plasma cannon
Chaos Marines can take Plasma cannons only for Dreadnoughts, and while their Dreadnoughts are a bit crazy - I never thought about it as about viable solution. But loyal Marines can give those fearsome template weapons even to simple tactical squads and Devastators. Why is that? I see 2 possible solutions:
1. All Chaos Plasma cannons got hot, and Dark Mechanicus don't want to build more of them. Well, it doesn't looks like true, because Plasma guns are still used in Chaos forces, and effectiveness of weapon worth the risks of using it.
2. Troop option appeared after Heresy, the same as Autocannon but from the other side.
Still, I am not sure, if you know something or have some ideas - comment please.

Multi-melta
Those things are accessible for Chaos Dreadnoughts too, but only for them. Maybe the story here is the same as with Plasma cannon? I'm not sure...

Still have no info
I have no info about some weapons, so if you know why they are accessible to first but not accessible to second - please tell me. They are:
Cyclone Missile launcher
Havoc Launcher