Can i travel 300 km using my Honda CB shine 125cc?

Of course, you can go with it. But, it will certainly gift you back pain. Still, you can enjoy a good ride following few steps.

Never make 300km ride in a single stretch.
Take rest and refresh yourself with tea or any food items at least in every 50 kms or whenever you feel to have a short break.
Avoid off roading. Try to trip on highways and better roads.
Don't fuel the gas tank fully. It may cause the stability in turns and corners.
It's better to ride within 60km which makes the bike controllable to you.
Try to wear a full-faced helmet.

Following these steps may help you to have a good and safe ride.

How many petol used in 300km

i also did this, from jhansi to lucknow, but had to take break multiple times. my bike was ktm duke 125