No, this is a very bad substitute. If you go to a 85 series tire which I highly recommend you do not do, you would need to install a 215/85-16. Another good substitute that would work well is a 235/75-16.
265 70 16 is similar.
275/65-16 or 235/75-16 Either of these sizes is an excellent substitute.
Replace the tire
Yes , you can replace a 205 50r 16 with a 205 60 r 216. You must replace in pairs, not a single tire.
The best idea to replace a tire which has a whole in it is to replace it with a new one. Reason as to why you should replace it because the tire can wear out and blow out sooner with a whole in it.
No, you typically cannot replace a spoke without removing the tire.
Yes you can
Generally requires removing and dismounting the tire, replace TPMS sensor, remount tire, balance tire, re-install tire to vehicle, do the relearn tire position procedure.
You can not replace just the tire pressure sensor on a Boxster. You will need to replace the whole sensor. The sensor is located inside the tire assembly.
Yes, you can.
Yes you can
Yes you can