Probably it has been already answered here, but still:

a) Merging templars on Conclave fleet card

You can merge Templars on any planet (via Build order), even without a base on that planet. OK. But can you merge Templars placed on Conclave fleet card?

You can place them there legaly (as you build them) instead of placing them on a given planet. "Archon" Technology card says... "you can merge... on the active planet." I think, that it is not possible.

b) Collateral damage.

Suppose a following situation:

Terran player controls a 2-area planet. In one area has a base (but this area is otherwise empty), in the other area he has some his units. Protoss player wants to use his Reaver with collateral damage tech-card to mobilize to the area with terran base and destroy it immediately (before he moves it to the other area via mobilize order).

But as rules say Collateral damage is activated only during a battle and in this case no battle will occur and therefore terran base will survive even if Reaver ocuppies that area (and supposing the Terran will move it to an adjacent area).

Similar problem is with an infesting of a terran base with a queen. Is in this case also needy for a battle to occur or can a queen do it even if the area with a terran base is empty?

Thanks for your answers.

A) if the templars are on conclave fleet you can't sacrifice them to build an Archon. However If you build an archon with templars on a planet you can place it on conclave fleet.

B) The reaver cannot kill the base with collateral damage without a battle. However Corey did clarify that a queen can infest a command center without a battle. I think the main difference between them is that the collateral damage is on a combat card but infested command center tech is out in play.

A) True.

B) Notice there are some cards which placed in Play Area ("Heroic Strategy" EC and Mengsk Stage III LC) provide some units with Collateral Damage. But even in that case they also have to be triggered during battle.