Just two questions

Currently I have 99 agony resistance. I heard that if someone invites you to a higher level instance, you can actually skip much of the grind to increase fractal lvl. My question is: Is it enough to enter the fractal in order to raise your level or do you have to complete it?

Second, I heard that in order to unlock the raid mastery track you need to kill a raid boss. However, I cannot find any info what kind of points it requires. Core or HoT ones? I want to plan ahead if I ever decide to go there, unlikely as it is.

I don't do fractals, but to answer the second one: It's HoT mastery points since raids were introduced with it

To my knowledge, you have to complete it. And while you can skip up to that level, you'll still need the appropriate amount of ar for agony to not 1 shot you. Additionally, it won't unlock that level for you, it will unlock the next level up from your current level

Raid masteries are hot content and therefore need hot mastery

To answer BOTH of your questions,

You can raise your Personal Fractal level by 1 everytime you complete a Fractal that has a level EQUAL TO or HIGHER than your current level.

Raid Masteries are hidden until unlocked by killing a Raid boss and Take Heart of Thorns Mastery Points to progress each step.

@EpicName.4523 said:Currently I have 99 agony resistance. I heard that if someone invites you to a higher level instance, you can actually skip much of the grind to increase fractal lvl. My question is: Is it enough to enter the fractal in order to raise your level or do you have to complete it?

as @Haleydawn.3764 said, doing higher level fractal than what's available to you will only increase your available fractal level 1 at a time

The thing is, you would want to do all of them to get fractal level completion achievement; so rather than do them later on, might well do them now to unlock the next level