Idk the answer to question 1 but I know the answer to question 2

KILL THEM or don't get seen

@Spider33

Yo!

1. Normally a Codex appears when you skulljack an ADVENT Officer. It will spawn on the same turn.

2. Stun Lancers can be nasty - they can knock unconscious a perfectly healthy unit (this is at least so on the Legend difficulty). Their melee attack can be disabled, if you disorient them with a flashbang or set them on fire. In my opinion this enemy unit must be a priority if he can reach your units with the stun prod. He can outrun and hit any XCOM unit due to having 14 mobility (12 on easy). On the low side is his low hitchance - only 65% - but his melee attack gets +10% Aim bonus. If you can't kill him before he gets to your squadmates, try assisting a most likely target with Specialist's Aid Protocol (grants +20 Defense) and hunker the soldier down (gives +30 Defense and also 50% Dodge chance for halved damaged -- don't know if Dodge has a hidden mechanic of disabling or reducing negative status effect chances); however, enemy might re-prioritize the initial target to someone else reachable with less defense.

Tysm!!

XCOM 2 is a tough game: I learned that in my first playthrough ... and afterwards, too! ;)

If you would need to know anything else about the game, don't hesitate to post questions here or in any other thread - I will try to answer to the best capacity of my knowledge. :)

Having a Bladestorm Ranger as your front most unit is a good way do deal with Lancers, but it's unlocked later in the ability tree. Bladestorm makes your Ranger attack any units that gets close to them, countering all malee units.

Besides the Bladestorm ability being unlocked later, it doesn't have 100% accuracy. It is either the blade attack doesn't get the +20% Aim bonus from a sword weapon (as regular Slash attacks) or there is a penalty (similar to Overwatch shots), though I suppose the former is the case. And maximum Aim stat for a Ranger is 80 IIRC, while Blademaster gives +10% Aim (don't know if the accuracy bonus is active with the Bladestorm) - that's why a Ranger is not guaranteed to hit with the Bladestorm.

In War of the Chosen though, Templar's Rend always hits (with Bladestorm as well).

On a side note, there is a Hellweave utility item vest. To a big disappointment, it is activated only after an attack was performed by a hostile unit. So, it is not a counter to Lancer, or Chryssalid, or any other melee enjoying units.

So, basically a Lancer is a priority for a kill. Flashbang is helpful in the early game with 4-unit squad, low Aim and lack of useful Abilities. They are often killed with a Ranger with a Blademaster skill (~70 Aim + 20% Slash attack Aim + 10% Aim from Blademaster) or with a shotgun (it has high accuracy bonus, up to +40% Aim, at close range), either with Run and Gun ability or without.