Questions about Tzeentch

[Nuradin]

So I was planning on starting a Tzeentch army! Mostly because I am looking for a caster heavy army. Something that can win matches by casting spells.

But when I google a number of questions arise. Questions my google-foo is not strong enough to answer. So thought I would create a membership here and ask all you all knowing people
Bear in mind that I have just started and don't know anything about any rules!

Question 1:
The lore of change and lore of fate spells. What are the rules regarding these? Can they be cast once per turn or once per unit? Is it the same with say mystic shield?

Question 2:
I've seen lists from the cancon tournament and almost every tzeentch player had around 300 points in reserve. In an army with pink horrors as battle line (I love those models, so would like to run a demon army), how are those 300 points used? Are they used to split the pink horrors into blue horrors? are they used for the Tzaangor Shaman special? Or the pink horror battleshock thingie? Or simply to summon something else?
I understand that those points can be used for either, but I am now looking for the specific way they were used in this particular case! I am interested because I want to know how the tactics for such an army would work.

I am sure more questions will come over time, but I thank you all in advance

Regards

[Skreech Verminking]

Answering Question one: in warhammer aos, a spell can only be cast once per turn and not once per unit.

Question 2:  yes, many players use does points to split their blue and pink horrors, as well as to block units with some summoned daemons from charging your Hero’s, if they should come to close. But you can also use it to summon some Chaos spawns, which then can lock themselves into combat, which literally means for you, another good round of blasting your foe to death.

So good luck to you and have fun playing ??