I am stuck finding Hannah but someone who answered another message gave me some ideas how to do it, but what I want to know is how to go back to a previous game since the game is autosaves? I need to go back to get the thing to open the vent. But how would I know which save that was and where can I find it?

The Chapters save system is not great, so prepare for fiddling.

In principle, you go to the menu and choose "load". Each time you pass an autosave point (usually around the major choices), the game creates a save file. The save files themselves convey bits of information by

(a) their individual names (places and events)
(b) thumbnail pictures and
(c) the time the save occurred

But it's still difficult to choose the correct one. Often you end up loading a save immediately after the scene you wanted to experience again. Experiments are of the essence, unfortunately.

Are you bug-stuck (i.e. adbot not moving around) or do you want to change a choice you've made?

Best of luck in any case! ;)

Thanks for your reply.I agree saved is not great. I would say it is very bad in the case you want to go back to a saved game. I wanted to go back to try to do something differently. I will try your suggestions and hope for the best. Ive come across a few bugs but got past them. Firt time posting here, hope I did this right. Thanks again.