overvoltage protection circuit problem!!!

can my overvoltage protection circuit connect in this way?

the voltage input, 'V in' go through the voltage regulator, which are Zener diode D7 series with Resistor R2 showing in the attachment. Zener diode D8 connect parallel with D7 and act as the protection or prevent of reverse polarity of voltage and current going through output.

to consider the overvoltage, i add the thyristor parallel with D8, can it be connected in this way?

Don't double post.

Over/Reverse

There are a few thing missing. If it is a 5 volt supply I would use a zener above 5 volts. Maybe 5.6v. Add a capacitor say 25 ufd. from the junction of the zener and the resistor for good trigger.
Is there a fuse somewhere? How big?
The reverse voltage won't work as it won't trigger the SCR. You might consider a shocky diode in the 5volt line for the reverse voltage if you can stand the voltage drop under normal conditions.