I found about 4 projectile weapons (Gloo Gun, Pistol, Shotgun, Nerf-style crossbow lol) in the demo, plus numerous grenade types, all of which can be used in their own way. 

I also played around with weapon upgrades and making supplies and materials using the machines in Morgan's office.

I was able to get past some doors barricaded with Level 3 weight objects by chucking explosive canisters at them and dislodging them that way. You could also throw other heavy objects at them, or use your Gloo Gun foam to push slightly lighter objects to the side.

If you shoot holes in gas pipes to create flame jets, you can seal them back up with the gloo gun and shoot them against to restart the fire.

I was able to enter Morgan's office a second way this time - use whatever means necessary to get up to the walkway opposite the office on the other side of the lobby, then climb over the railing and walk on top of the large sculpture hanging from the ceiling to reach the office window. Use the wrench to smash the window and you can completely skip the stairs on the right of the lobby. 

On the back of many doors there is a lock override which allows you to keep the door locked after you enter - meaning you won't get ambushed. You can use a bouncing foam dart to shoot through a window of a locked room and hit the button from the inside to open the door, allowing you to get in without using a keycard. (This wasn't my idea - I saw it on reddit and my jaw dropped!).

I saw a few enemy types - Mimics, Phantoms and...glowing phantoms? The phantoms talk to themselves if you wait and listen and it becomes apparent they used to be human. Indeed, I noticed that the ones that talked had crew-member names above their heads. I didn't pay attention to whether that was instant of whether it changed because I followed them. Glowing phantoms seemed far more deadly and I died a couple of times working out how to beat the fucker - got there eventually. They also wreck turrets embarrassingly quickly.

I was also able to get to a few locations using boxes and foam to create platforms or shorten a jump. 

The first instance of something appearing wrong is the skybox in the helicopter glitching for a split second. However, if you talk to the mechanic in your building after you first put on your suit, you can actually get the Truman show vibe then and there - she'll start of with normal conversation but, if you keep talking to her, will slowly get more and more disconcerted, telling you:

"You're supposed to keep going"
"You're gonna get me in trouble"
"I'm not allowed to talk to you anymore"

There's a safe at the beginning of the game after you first escape your room which has a code on the whiteboard - the problem is that the code has been wiped off. Later, in your office, when you view a video of you talking to yourself in the present, look to your left and you will see the whiteboard as it was - code and all. 

There's a LOT of touches like the above in this game - most of the time the things i discovered weren't of any great significance, they just added depth to the environment. For example, after escaping your room - when you enter the reception, go into the elevator and click "Roof" and see what happens.

In the end there were still 2 doors I wasn't able to get into but, apparently, you can only get in via glitching and then can't get out, so no loss there.