Hii..
As mentioned here your age and about your degree courses ...so with these things .....yes you are eligible to seat in SSC.... as a for age SSC eligibility is like a candidate have  not to be  less than 18 years old and not more than 32 years old... But it's vary from post to post... so as mentioned that you are  18 years old and nine month.. so yes you are eligible for that  ...also as mentioned that you have a civil diploma degree so you have a bachelor degree ..so eligible for SSC exam
All the best!!