Yes
There is nothing that prohibits this interaction. The ranged attacks made from Volley count as weapon attacks, so any of them can be used as the "trigger" for Horde Breaker.
Note however that Horde Breaker allows you to do this only once on each of your turns, so you can't trigger it on each of the Volley attacks, but only on one.
In your example, you can attack each of C1, C2, and C3 once from Volley, and another one of them a second time, as long as the target of the Horde Breaker attack is within 5 feet of any of the original targets (so if C3 is further away than 5 ft from both C1 and C2, C3 will not be eligible for the Horde Breaker extra attack).
Conjure Barrage is not a ranged weapon attack.
This does not work because "ranged weapon attack" in D&D 5e is a term of art--it refers to a specific piece of the rules, and not necessarily the underlying fiction. While the effect of conjure barrage may intuitively seem like a ranged weapon attack, it is not a "ranged weapon attack" as far as the rules are considered.
A "ranged weapon attack" is partially defined on PHB 194:
When you make an attack, your attack roll determines whether the attack hits or misses. To make an attack roll, roll a d20 and add the appropriate modifiers.
On the other hand, conjure barrage asks for a saving throw—it is the target that rolls the dice in that situation. Because it calls for a saving throw, and you don't make the attack, it doesn't work.
Compare this situation to a spell like fire bolt, which asks you to make a ranged spell attack. In this case, you're making an attack, so you roll the d20, but it's still not a "ranged weapon attack" because it's a "ranged spell attack".
Essentially, you need to fulfill all three words of the phrase. You must make an attack (you roll the attack roll), at range, using a weapon.
Note that you can't cast those spells in one turn.
The wording in your question is a bit ambiguous, but it's important to note that you can't cast both of those spells in one turn, because that would require a bonus action spell and a 3rd level spell. PHB 202 states, (emphasis added)
A spell cast with a bonus action is especially swift. You must use a bonus action on your turn to cast the spell, provided that you haven’t already taken a bonus action this turn. You can’t cast another spell during the same turn, except for a cantrip with a casting time of 1 action.
Best Answer
Yes. Conjure Volley will damage lycanthropes.
Here's the relevant part of the Conjure Volley spell description:
The weapons don't do the damage, the spell does.
Here are the immunities for a werewolf (SRD, p. 331):
Conjure Volley isn't a 'nonmagical attack'. It's not an attack of any kind: it's a spell that does damage.
Contrast with a black pudding, which is just immune to slashing damage. Conjure Volley using (say) handaxes would do zero damage to a black pudding, but full damage to a werewolf.