What are the strategies to getting past a stationary guard that is watching the door?

Solution 1:

The door itself from my side has squares on left and right of it blocked. So when I open the door I:

• Immediately visible, and
• Cannot hide after being seen

OK, well you could of opened the door - letting the guard see you, become alerted and go into overwatch - then close the door. This will safely break the line of sight so the agent doeso not get shot and let the agent move away. This will also draw the guard to move through the door to hunt the agent, be warned that it is possible they might kick that door down (breaking it forever) so do not stand behind it.

Another option for getting the guard to move would be to make an agent run as close as possible to the guard, possibly making him move to investigate the sound. A similar approach would be to use the ping Incognita program to create a sound. If you can evade this guard without KO'ing them they would eventually return to their original location, non-alerted.

What are the penalties for leaving an agent behind? That is if I do not drag it to the teleporter?

Any KO'ed agent left behind is considered MIA and is lost for the remainder of that game, the equipment they were carrying is lost with them. If you cannot revive an agent, you can drag them to the exit (it which case they will be ready as normal for the next mission) or take their equipment.

I think it might (might ^(possibly)) be possible to rescue that specific agent from a later detention centre mission, but I've never had the opportunity to test this.

Is guard placement mostly random...

I understand it's very random, it's quite possible to get situations where it's not possible to pass undetected.

Note that the higher difficultly settings enable guard patrol routes that pass through multiple rooms and routes that can enter the starting room - so having a guard stood somewhere awkward is not the most dangerous behaviour to watch out for.