Feed the Fish
To get this challenge, go to the area where the exit to Research and Development is located at the north end of the map. At the very tip of the map, you should see a fish tank sitting on a desk. All you have to do is go up to the tank and interact with it to complete the challenge.
Corporal Bob is a random spawn in the Hyperion Hub and will eventually drop a flame turret if he’s alive for too long. He isn’t tied to any mission, so this can be gotten at anytime and all you need to do is kill him before he drops the turret. This might be easier if you wait until you’re a higher level, as his own level doesn’t scale to yours.
Oh, the Humanity
You will need to shoot the target on the ship that is flying around the large area just south of the door that leads to Research and Development. The ship flies around pretty slowly and the target you need to hit is the blue camera thing on the side of the ship, which is near the top.
In the southwest corner of the map, you should see a stream that will lead to a waterfall. This is the same waterfall that one of the ECHO recordings is on for the Boarding Party optional mission. However, you cannot jump onto the waterfall from the ground below, so you’ll need another way onto it. Along the same wall as the waterfall is a switch you can hit to open a secret door, which will allow you to reach the top of the waterfall. Just jump off the waterfall and into the water below to complete the challenge.
In the northern part of the Hub, in the large area where you see the ship for Oh, the Humanity challenge and right next to Dean for the Hot Head optional mission, you will see some stairs. Go up those stairs and across the bridge to some train tracks (avoid the incoming trains). Run south along the tracks and onto the platform on the right to complete the challenge.
You need to enter all of the shops in the area, of which there’s only three. In fact, you will enter two of them during missions, with one being Home Sweet Home and the other during the Kill Meg optional mission. That leaves one more, which is beneath the Flowers 407 sign, but this one doesn’t actually open. You can simply touch the door in order for it to count for the challenge.