No? The dark charm known as the Killing Curse can pierce barriers purely due to its own hax. All Charms in HP work afterall by adding certain properties upon an object or creature according to The Standard Book of Spells, Grade 1.
No, they can't and I have to give it to Siriel(for once) in that only Voldemort has ever shown the ability to have a Killing Curse go through a Charm. No one else has shown that capability at all.
Properties here can be anything really, from a natural force to even a conceptual idea used to power the Patronus. The protego charm, for instance, imposes the property of "protection" around its target, allowing any wizard or witch to be heavily resistant to a multitude of magic that targets them, no matter how unorthodox. In the case of the killing curse, the author implicates the AK works by imposing the property of death upon the target, given anyone who gets hit by it immediately drops dead without causing any injury to the body, and any trace of violence.
Uh yeah no, that's not how AK works... hell, that's not how any of the Forbidden Curses work. The whole reason why the Forbidden Curses exist and are so gamebreaking isn't that they exist, it's the fact that they are literally fueled by sheer negative emotions to such an unreal degree that Harry Potter seeing the person who killed his godfather right in front of him using Cruciatus couldn't do shit to Bellatrix past her fucking around because it wasn't "the right type of hate".
This also ignores that Protego is one of the strongest defensive spells in the franchise to the point the Ministry bought Fred and George's stuff because it literally has a Protego Charm on it.
It also explains how it was able to bypass protections granted by Protego, as the AK is effectively killing the protection at a conceptual level. On the other hand, Love, instead of a magic, in Harry Potter verse is a tangible primordial force that can be harnessed unconsciously by living beings to supersede natural forces like death. This is something Dumbledore states in the books when describing the study of Love in the Love room within the Department of Mysteries.
Okay, how does that mean AK goes through shields then? All it means is that it simply kills the shield but leaves the user alive... some killing curse right?
Its also the reason why Harry's willing sacrifice to Voldemort during Deathly Hallows conferred Harry's allies a certain amount of protection, thus the spells Voldemort tried to place on them (even an AK) wouldn't work.
I am about 1000% certain that is some absolute bullshit because that is never a canonical thing or else Sirius wouldn't be fucking dead at Order of The Phoenix... or the Weasleys in Deathly Hallows... or most of the people Harry met that died between those two and during DH!
Furthermore, I don't think you can intercept an AK midair with an Experlliarmus or Stupedy unless
a: Priori Incantatem is triggered, where two wands recognize each other as "brothers" and refused to attack one another.
b: You win over the loyalty of the wand opposing you, hence no matter what spell is fired at you, it will never harm you. Its the reason why Voldemort's AK via the Elder Wand could never harm Harry during the final battle.
So the Methode's barrier you mentioned below wouldn't work.
Yeah, this is some worthless ass NLF exceptions that again has no basis in canon and completely misunderstanding Priori Incantatem being why Harry wasn't dead at The Goblet of Fire...
I feel the idea that Frierenverse's defense magic would allow it to block really any spell in HP, especially the AK, quite ludicrous given the intrinsic differences in how the magic systems of both verses operate. For instance, you mentioned previously defensive spells in Frieren specifically attune themselves precisely to the oncoming spell and then apply equal power in the opposite direction. From I recall in chapter 93 of the manga, this attunation is tailored to the mana of the incoming spell.
Then what is the fucking point about mentioning ANY OF THE ABOVE?! Frieren's Magic System isn't even that strong compared to some other series with Wizards in it(Like D&D for the easiest dunk or Fairy Tail/Eden's Zero/Rave Master) so again, what is the point of acting as if people sleep on Harry Potter, then just mention that shit?
How would that work via the spells from the HP verse, who don't have any "mana" or magical source powering them? I don't think the energy released by wands in HP is even mana, though it should be noted adult wizards and witches from Fantastic Beasts and Where to Find Them series mostly don't release beams of energy when evoking their spells, more so their wand tip just glows, and reality tends to bend over to evoke the effect.
Funny because I remember a few times that Harry and Co. being winded from casting spells quite a few times... so it has to take from someone or something...