Design

Try solving previous papers and see if you score up to the level. If yes then practice similar questions from different exam papers. They are no reliable study materials for UCEED. I would recommend this blog for resources =&get; Materials for UCEED exam preparation
You may also refer to my answers o

NIFT Entrance Test is taken by candidates to secure admissions into various design programmes on offer at National Institute of Fashion Technology (NIFT). This fashion design entrance exam is conducted at a national level for candidates seeking admissions in design, management and technology program

UCEED exam is for admission into designing course. It is related to engineering and it is being conducted by IIT Bombay and some other IITs as well. You can refer to below links for more details regarding this exam.
https://www.google.co.in/amp/s/www.shiksha.com/design/industrial-product-design/exams

You may pursue the same course from here:
https://www.iidesign.co.in/automotive_biw_design_course.php

You will have to check the same after going to institute only, as they only disclose fee to the students who wish to take admission there.

Once you have completed your course for jewellery designing, there will be ample of opportunities in both the private and public sectors both. There are government departments such as Museums, Antique Houses, Mines and many more. The government also runs test through UPSC, SSC, PSC, etc.
Apart from

Yes, you can. But, you will only be admitted on the basis of your 12th.

The institute changes fee every year, so please check the same with institute only.