As
@Jcakes said, the 1st and last photos, Blue Tongue Lizards are great natives. They control a lot of pest/insect populations, and aren't venomous. If harassed, they can offer a nasty bite and probably lead to bacterial infections from their mouths/teeth, but honestly, they like their space and will disappear among the grasses pretty quickly. They rarely chase. A great sight whenever I see them, but often missed by seconds as they escape quickly.
And yes, the second photo, the eastern brown snake is definitely venomous, and quite dangerous. It will tend to avoid confrontation, and prefer to slither away unless cornered or feeling protective. This particular one did not want to move away, and would defend the area. I got several photos approaching it, only keeping the best. This one was the best, where it reared up, absolute warning that I was getting too close and it was not in the mood to move away. Sadly the face is slightly out of focus, but... At that point, I was not willing to even try a second photo of it, as it was really annoyed. With that warning, usually the last from this type of snake, it was time to give it the space it wanted and deserves, and back away.
As Cakes mentioned, Tiger snakes are also very bad, venomous, and very distinctive. They tend to be more dangerous, as where an Easter Brown Snake will tend to retreat and avoid contact whenever possible, the Tiger Snake will actually chase a target that gets too close, for quite a long distance, including the ability to climb trees to chase a target. Luckily, they are still rare in urban areas, but are definitely possible to encounter in grasslands and bushlands when hiking. That said, I personally really would prefer to protect the remains of all of their habitats, and leave them in peace.