Plagiarism

can someone tell me how plagiarism works for hiring contests .Like if question is same as same as question on their website if i copy the solution of any user
so can this is considered in plag.
if i changed a syntax or use other lang.

It depends. If you’re caught regarding this reason, you can send an email to the site admins. If you’re really not at fault, the admins would surely help you a way out.