Kindly advice me if there is any wrong by adding urea solution (with water) instead of dry urea to crops like cauliflower, potato, tomato, bottle gourd, banana etc.
What is the method you are planning to add? If via drip, then it is very good. But dont give overdose, divide total dose over the crop duration, like give small quantities every 3 days or every time you give water.
Foliar Spray for such large quantity is not recommended, you can add 0.5% in every spray you do to give plant healthy look and instant rejuvenation.
I dont see any other method to give in water form.