1- Anarchists start from the individual whereas marxists start from the class as a whole. This is the major, starting theoretical difference between the two. Accordingly anarchists take an individualist position. Some anarchists may rightly point out that these hyper-individualist anarchists are not real anarchists or not representative, but they still exist and still claim anarchism, because anarchism has no platform and single coherent body of theory because, again, anarchism is individualist. Platformism, which was an attempt around the time of the october revolution to rally anarchists under a political platform (with a programme and everything), failed as quickly as it started.
In my experience anarchists also tend to take a contradictory position on everything just so they can stick it to the man. I know an anarchist IRL and he's insufferable, his whole thing is just saying the opposite of whatever a political group promotes. This includes the neoliberal state but also the marxists.
As for hate, depends what you mean by hate specifically but because of this individualist position they go against any form of authority that is not their own 🤷♂️
2- they can be yes. ultra-leftism is a label used to mean dogmatism or adventurism, there's a little more history to it but that's how it's mostly used today. Ultra is broader though, for example leftcoms (leftcoms are usually Bordigists if you want to get into it) are ultras too. Ultra generally means unwilling to budge on the theory (i.e. the dogmatism).
If you're asking because of how we have !shitreactionariessay@lemmygrad.ml and !shitultrassay@lemmygrad.ml on lemmygrad, this was mostly to make a difference between right-wingers/centrists and left-wingers in two different communities that already existed, that's why it's named shit ultras say.
3- Trotskyists are out there doing their own weird thing lol. Some of them could be considered ultras but I mainly see them as a cult I'm not gonna lie. So much weirdness around trots, like how many of them became neocons. They usually appeal to academics (seriously look in trot parties it's mostly academics), I guess because in a way it allows them to claim marxism without the baggage surrounding it. they're not necessarily always wrong, I've appreciated some historical writings of trotskyists. But as soon as it gets a little bit too close to the 20th century and beyond, it's just brainworms lol.
Do they dislike marxists? Not necessarily, but they have this entire thing about stalinism and the purity of lenin and trotsky had completely nonsensical theory mired in his petty bouge upbringing and point of view. Permanent revolution was dumb, it would have destroyed the revolution, and it's a good thing the party did not listen to him (he wanted to repress the peasantry instead of allying with them on the off-chance that the german workers, who were close to having their own revolution at the time but was put down by the proto-nazis, would come to their help during the repression). So clearly with a theory so wrong you have to wonder why people would still claim his legacy - it's clearly not for the theory.
They also just have trotsky on their mouth and no one else it's weird. Sometimes they might bring up Marx, Engels or even Lenin (because of the split between Trotsky and Stalin that they tie back to Lenin and the faked "will") and they don't necessarily handle them wrong, it's just you can tell it's sort of an after-thought or quote mining instead of putting Marx back as a whole person who lived and wrote in a certain context. They really just want to talk about Trotsky all the time when the guy was a huge failson. They claim it was stalinist repression to purge him from the party when Stalin was obviously not the only one deciding this lol. Everyone hated him by that point in the CPSU. Pass.
4- Maoism was invented by Gonzalo of the Shining Path in the 80s, which he envisioned as the next stage of communist theory just like we had Stalin synthesize marxism-leninism with the advances made by Lenin. This is highly disputed because an exhaustive reading of Mao will show he did not do things sufficiently differently from Lenin and the bolsheviks to warrant his praxis being considered a universal, settled advancement over marxism-leninism. A lot of what Mao operated on was already done by the Bolsheviks (e.g. organizing the peasantry as we saw), he just pushed it a little bit deeper and according to China's material conditions. So the point of promoting MLM was clearly different than the stated objective. Some can be placed back to the Sino-Soviet split, according to Andréo Matias the CIA distributed Mao's Quotations in south american universities back at the time of the split. A lot of maoists I know seem to exist entirely online and are very disturbed individuals, wanting to commit violence for the slightest perceived offense on them. Jose Sison, of the CPP (Philippines) and the NPA later softly distanced himself from maoism without saying it as such, and this got him the ire of the maoists who denounced him -- reminder that maoism as gonzalo synthesized it has not yet produced a successful revolution, and has only existed since the 80s. It's kinda putting the cart before the horse. You could call them adventurists.
Like I don't deny protracted warfare exists (it happened in China and in Vietnam for two examples), I just don't think that it's something you provoke but rather something you are dealt.
But yeah Sison explained that in the west because of the military apparatus our protracted war would first begin with our protests and marches before being armed etc. this is just normal lenin stuff. Whether you want to consider that part of the struggle protracted people's war is up to you. But that's one thing that got other (western) maoists to denounce him despite that he was the only one out there actually waging revolution. Or, well, Sison had been living in 'exile' the Netherlands for decades while the NPA continued its operations in the Philippines, so I don't know if I would say he was actually out there doing stuff lol. But regardless, Losurdo was right: in the west our marxism is mostly theoretical and becomes concerned with our theoretical purity and adherence to the "rules". You have Swedish maoists, who have probably never once held a gun in their hands, giving lessons to Sison on how to conduct protracted warfare lol. They may be right theoretically but theory is meant to be applied.
Hoxhaists are ultras in a similar way as trots. Quote-mining a lot and dogmatic on their "anti-revisionism" because hoxha kept talking about being "anti-revisionist" because he was salty about stuff. China stops sending him money aid, he calls them revisionist. Stalin dies, he calls USSR revisionist. Once again refusing to place it back in the context in which Hoxha and his writings existed. That's a problem of depending too much on a single figure imo, but it's obviously also deeper than just that. Like all I ever see them do is rant about revisionism and basing it all entirely on one single figure -- not even a person, because I never see them talk about Hoxha as a person like where he came from, how he came to lead Albania and what he did there etc -- just the safety of having an authority figure give them justification to call everyone else revisionist. Well I'm against revisionism too, I just think that China isn't revisionist lol.
We follow Lenin because he fucking succeeded, that's what it boils down to. So clearly he knows a thing or two about making socialism happen.