Is there a vegetarian natural food that can supplement level of B12 naturally without depending on non-veg ?

Try having a combination of dry fruits, nuts and seeds daily. You can compare the nutritional values if you're really focused on b12. Also add some milk based products to the day. If you need higher dose consider having supplements/tablets. Anything that has b12 with RDA limit from a single day to a few days is safe to take.

Nope.

Milk contains vitamin B12, apart from these fermented foods such as tempeh and kimchi contain a considerable amount of vitamin B12

You can take b12 tablets without prescription. Or milk 2 large glasses.

Sprouts , soy, soaked fig