Transfer in case of industrial training

I am a ca final student in 2nd year of articleship working with a small firm .  I want to persue industrial training in my 3rd year of articleship however my principal says that he won't allow such although I have  not signed any restriction agreement to serve articleship till 3rd year . Can I give a prior notice of 3 months as per the regulation and apply for form 120 based on available records with me . And from where shall I get form 120 as such forms are not available on ssp portal .. a genuine reply would be much appreciated m thankyou