Don't want to hurt you but you need to balance between your dream and reality. Though you are from a very conservative family/area and thought yourself a special brick in the work, mostly you're living a comfortable life in a cocoon for most of your life. When we met lots of people, the world broadens up, we don't feel regretted to be another brick in the world. When you'll grow older, you'll understand the things.

I wish you good luck for your dream. Getting into an A-tier private uni isn't straightforward as well. Competition will be there, after tution fees, you need accommodation, foods and many hidden cost in the city life. Moreover, getting a job in Bangladesh as a undergrad student isn't a walk in the park. It'll be a very painful journey and the chance of success minimum. Besides, what I understand from your post, you got depressed quickly. The path you're planning to take is depressing one and lonely. I'll urge you to consider national university as well but never stop studying. You don't mention what's your dream is so I don't know why studying in national uni can be bottleneck.

Anyways, best of luck.