Thank you for sharing your concerns on this platform. I can understand how you must be feeling and how discouraged you must have felt when you did not get the raise you deserve.
Startup's usually do pay less when it comes to salary, as they have just started and need a lot of time to establish and make themselves known in the corporate world. But even after working in a startup for only a year, and getting your salary hiked by 150% is still very commendable and shows how good you must be at your work and how hard working you must truly be.
I can understand why you would have wanted an immediate shift and decided to leave the company you are in and pay back the required amount. Asking your parents for help in financial matters would not have been easier on you either, and must have made you feel very bad. What you can do is start saving and in time return the amount you borrowed from parents to them.
I understand that must feel that earning 28K when you are 24 years old, can make you feel quite low, but what you need to understand is that 28K is still quite good for someone who has only 1 year of experience. I understand you must be anxious about starting in the new company due to the mixed reviews and must be having second thoughts. What you can do is have a plan. Decide if you like working there, and if not, how long you can stay there. If you decide to leave in a year, then start looking for a new job at least 3-4 months before the year is up. Update your profile on various Job searching sites and mention your notice period to avoid having to pay a fine.
It is understandable why you must be feeling like a loser, but you are not. You are a very hard working person and have a bright future ahead of you with loads of opportunities. It might be looking not very good at the moment, but it will be brighter tomorrow. Have hope and do your best.