hi bhavik,
i think you are not eligible to give GUJCET,it will have PCM subject questions from gujarat board(senior secondary/+2).since you're a diploma holder,you can't give GUJCET.So the possibility of diploma holders to give GUJCET is very less.
if you give GUJCET, then you'll be go to the first year of engineering course not will be considered as Laterl entry.
.I suggest you to check its requirements to give that exam through this below link.
but you can get lateral entry admission through the exam named LEET.
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