He normally assumes the body of a girl, but with no genitals. So no.

don't do it

Manga already shows the first half (or maybe third) or so... Rageth's translation of the synopsis covers most of the rest of the volume, with Rimuru ending up basically creating the beginning of a monster city

Something threatens the area: An orc tribe's leader evolved (or was born as, don't remember which) into an Orc Lord, a powerful leadership type monster that leads a huge army of orcs to basically rampage across a large area, killing and eating everything in their path like a giant swarm of humanoid locusts. Rimuru gathers his own forces, the nearby lizardmen tribe, and a group of Oni who were survivors of the Orc hordes to counter this threat.

The 2 female Oni, Syuuna and Shion find Rimuru completely adorable and tries to hug/snuggle him whenever they can. They'd be 2 of the "harem" mentioned earlier.

Rimuru's activities has drawn attention from the various world powers, include a number of Demon Lords who came together in a council to discuss what to do. With Verudora gone, the area where he was (which is where Rimuru's city is) has lost its reason for being a forbidden territory, and one of the Demon Lords, Milim (the girl in the image posted earlier), decides to personally investigate for herself.

Milim is a dragon and, despite her looks, is actually one of the oldest and strongest Demon Lords in terms of destructive power. She came to the city basically looking for a fight, only Rimuru instead diplomaced her into trying out the various new social, technological, and cultural innovations that he has introduced. Milim was completely hooked and pretty much got tamed, making her the 3rd member of the "harem", and she ends up freeloading in the city and playing with Rimuru the whole time.

1.Why doesn't he free Verudora ?
2.Has he, in the light novel, also commanded his subordinate to not hurt humans as he does in the web novel ?this one is just because i'm pretty bored of MC who glorify humans as the race attacked by "evil monsters"
3.what did he predate and what skills does he gain?

1)He will free him later, he needs more time
2)read only wn so no idea
3)human girl with fire demon possesion(?), shadow _tempest wolf)was a normal one but its form evolved together rest of wolves), some sort of strong demon snake, the leader of orcs, a demon bat
Later he will be able to "eat" attacks too

Does he acquire "infinity prison" and become the great slime god able to instill fear to even Verudora?

he was really pissed of he massacres an army of 10,000 to obtains the "True"qualifications for Satan rank.(requires you to kill 10,000 people by own hands)

no he didn't. And they're pretty much equal to each other. And later they kinda became "one". because of the Dragon body was impossible to remove from the prison but they can remove his mind and soul. so what he did with split himself up and gave him a slime body equal to his (he's already high-level Satan rank at this point.)
so then walking around makes them look like twins.
the dragon expecially love earth knowledge so he's after he copied his memory he started making moves based on anime and manga. his favorite thing to do is suppress his energy all the way to the lowest and then when someone talks s*** he releases it all like a Super so much because he lowers it so much people and even other satan class people can't normally feel it so they tend to look down on him then SURPRISE BITCH.
( it's his new favorite sadistic hobby)