Metallurgy

Yes, you can take entrance exams for B.Tech and since you have already done Diploma in metallurgy engineering, so you can directly take admission in the B.Tech 2nd year through lateral entry.

Can you mention the name of college in which you want to take admission?

You should always ask the question in a lucid manner, kindly clarify your question.

You can continue your B.Tech or you can join any job.

Requirements vary from university to university. You must take GRE and TOEFL or IELTS exam depending on the country in which you want to pursue your MS.

ITI is the minimum eligibility to become a motorman.

Both are very different streams. You can opt for the engineering branch that you love the most and passionate about and analyze the future work conditions, scope and growth prospects before taking admission.
You can also opt for psychometric test comprising of aptitude, personality and career interest to clear confusion.