Limited.
Action: When your opponent declares at least 1 defender against your attack, put target unit in your discard pile into play in your battlefield declared as an attacker. At the end of the phase, sacrifice all units that attacked this phase.

Action: When this unit attacks, reveal the top card of your deck. If the revealed card is a HE unit with a printed cost of 2 or lower, put it into your battlefield, attacking.

Action: When this unit attacks, reveal the top card of your deck. If the revealed card is a HE unit with a printed cost of 3 or lower, put it into your battlefield, attacking.

Can units that heve been put into battlefield attacking trigger their actions: "when this unit attacks…"?

It can, but Reckless Attack is a chaos tatic while Tiranoc Chariot and Korhil are still high elf units. So you can't combine these cards.

.Crux. said:

I know I can't combine these cards, they just have the same mechanic. What I meant is do units played in such manner (without being declared as attackers) trigger theirs  "when this unit attacks…" actions (Blood Dragon Knight, Swarm of Bats etc.).

If you put into play a unit via Reckless Attack it is also decleared as an attacker (if this point may be relevant to you). 

Effects that trigger during the declaration phase or if a unit still attacks are Triggered Actions. So this fact is relevant for this situation (FAQ 1.9):  If this trigger condition is met during the resolution of other effects (or outside of an Action Window) then the Triggered Action must be played during the first available opportunity once an Action Window opens, or it cannot be played at all. 

I think they can still trigger their abilities.  It triggers off of "when it attacks" rather than "when it becomes an attacker" or "when it is declared as an attacker".  And it comes into play attacking, so it basically just triggers with the same timing as a "when this unit enters play" effect.

So it just as Crux said and I thought, thanks Entropy.