Hey there !

As you told that you had passed 12th from open school thats absolutely fine.

For getting eligible for the communication constable post ,firstly  must possess pass in SSC or any other examination recognized by the State Government as being equivalent to SSC and must possess Industrial Training Institutional Certificate in Electronic, Mechanic or Information
Technology and Electronic System Maintenance or Computer Operator and
Programming Assistant or Mechanic Consumer Electronics or Electrician .

Age  :-

min age 18 year - max age 22 year

there will be a physical test also you need to clear that aslo.

Application form are in online mode .

hope this will help you

Good luck!