I have never hacked or used any extra programs, but I will try and address the issues that you have brought up in the demo.
Tick 2000: That hallway is the most used on de_dust, I camped behind a box and domed the first 2 guys that weren't looking at me, not too crazy I don't think.
6900: Double hs again - First guy dies with me spraying while aiming at his legs, that is recoil and the second kill wasn't a headshot just a spray and kill.
12400: Knows to look down [footsteps plausible?] - After the fight in those main tunnels my whole team ran that way so I decided to check the long underway since we didn't have a single guy there. I jumped to check for someone and happened to see a guy, so I jumped again and sprayed to kill him.
16000: Tracing around corner - The first 2 guys you can see clear as day, I sprayed a little and killed them. The 3rd guy jumps to the right and I saw him do it and was ready for him when he peeked back out.
18500: Doesn't move gun, yet nearly all bullets are finding their mark - I sprayed and pulled my aimer underneath my targets, they were also being shot by my teammates. I don't know what hack you think I'm using to do this ... Magic bullets? I aim at one location and my bullets go somewhere else. At that tick I see recoil from a P90 ...
25400: 2nd Kill (last one), knows to look to his right – victim fired only 1 shot that would have indicated on radar - I killed a guy on the left and then checked the right to see if anyone was there ... I peeked, saw a guy and ducked back into the tunnel and then came out to shoot since now I knew where he was... I do this constantly and I'm sure many players do.
28800: Cursor zips to victim’s head - The cursor is on his chest, I sprayed and with recoil a bullet hit him in the head. Pretty sure everyone has seen recoil at work.
33000+33300+33800: sv_showimpacts - The kills in that underground tunnel were all spray kills, and like you suggest I turned on "sv_showimpacts" and my aimer is again pulled lower than the target and sprayed. With sv_showimpacts on you can see that like 70% of my bullets miss. All that can be seen from these ticks is that I spray a lot with a P90 and rely on the bullets to consistently hit above my crosshairs with my spray.
37000: 3 kills, sv_showimpacts - Again, I play a lot so I'm decent with the ak, I can't see how this is seen as hacks in any sort of way. If you're wondering how I hit guy behind the box, I did see him run behind it and assuming he didn't disappear I fired at the box to finish him off since I shot at him for a lil bit already. He also peeks from my left from behind the box and I readjusted my crosshairs to him there and when he ducks behind for the final time I shot at the box. Sv showimpacts clearly shows the first 2-3 bullets hit where I shot and the rest go in a random spray around my target.
39500: Crow kill – granted 1 hp - still hit the small hitbox on the first shot - The crow comes down the underpass shooting, I heard the shots so I looked down. I wasn't ready for a crow, but the crow gets stuck at the corner of that box, if you can't hit a crow that got stuck I don't know what to say.
41200: Waits for guy who would not have been on minimap, walls *** - There was 2 guys fighting my friend, he kills one and I come in and kill the other. The game should be over right? When it doesn't end and the guy who died second to last is alive the only place he could have resurrected is back at his spawn. If he had respawned at his corpse we would have seen him so that meant he was going to most likely take the most direct route back to help his friend who when he respawned was still alive. I waited at the spot and aimed where I knew he was most likely to come from.