I believe that when you applied for the visa, you specifically mentioned that you will be traveling with an adult whose name has to be specifically mentioned on your visa. The Gov.UK website clearly mentions that in case this adult is not with you, your entry will be denied.
When traveling to the UK with an adult (someone over the age of 18)
you’ll need to identify them in your visa application.
Their name will appear on your visa, and you’ll be refused entry to
the UK if you arrive in the UK without them.
Now, assuming your current case, the option which you suggested should work in theory. Albeit I won't say it is a safe option at all. Ideally, once you get to the UK, unless you break any laws there, you shouldn't be stopped while getting back to India.
On the other hand the correct way to do this is to change your visa into one which allows you to travel alone. Now, I'm not sure how this works in practice, but the Gov.UK site has a great section on traveling alone as on a Child Visitor Visa.
As per this section it should be possible for you to travel alone as long as,
Your parent or guardian will need to provide their:
- written consent for you to travel to the UK
- full contact details
They’ll also need to provide proof that you have somewhere suitable to
live during your stay in the UK, including:
- the name and date of birth of the person that you will be staying with
- an address where you will be living
- details of your relationship to the person who’ll be looking after you
- consent in writing so they can look after you during your stay in the UK