Yes you can apply for short service commission .But SSC (Short service commission ) vacancies are not regularly announced .Read news paper for their ads .

Bro the best trick to make good stories is to read good books and read healthy news in newspapers . stories , word associations test , sentence completion test is just used to check the psychology of candidate .So it is very important that first you should try to improve your psychology. how i can do this ? this is second question you will ask ,so here is an ans. psychology is basically a way to understand and to predict and to react after some observation. like if i show you a picture having fire and i want to write a story or tell me what you think about this pic , majority of people live in pakistan say that it is bomb blast etc , and very few said that it is summer camp fire.here is a difference of thinking.
Thats why it is very important to think optimistic and always try to see the positive side of the image. lets take another example
"after she saw a dead body ...." complete a story . a person having pessimistic thinking then he may be take above mention statement in a wrong way. but if a person having optimistic thinking he can write like this after she saw a dead body ,she feel her self very energetic because it was her first dissection ,Amna always want to be a doctor ..... and now from here you can start a healthy story.

this the way to make your stories better it is tricky isn't it ? :p well bro to think optimistic it is very important to make good friends , try to avoid news having some violence . read good books , watch army documentaries and yes practice to write stories , this will help you to improve your sentence structure. and try to write on blank papers . if you need any more guidance please add me on skype .

Best Regards