screen hinge loose tilts
Is possible to tighten the iMac screen hinge without completely dismantling the computer. some claim a plastic card pushed in above hinge with release a clip allowing asscess to torx screws ?
Simple solution: A rubber crutch tip placed between the monitor and the stand holds the monitor position securely and can be very easily adjusted in about 5 seconds. Cost: $0.29.
The newer iMacs have a newer foot design.
Your idea of a plastic card was the means to gain access to the foot screws to replace it for a VESA mount on the early '12 and older units. Sorry won't work here.
Here's some background: iMac 27" stand removal.
Given the age of your system I would try going to Apple for repairs.
I think that you can add glue and duck tape and it will fix it while quacking