BSc Hons and BSc Major are quite of a same. Although in BSc Major you get a BSc Minor degree with it and BSc Hons you read 2 subjects rather than your Hons subject as General Electives but you didn't get any separate certification for those electives.

BSc is a basic course which gives you just superficial about the subject you choose and not in depth. The pressure is very less for this course.

Now if you need to prepare for Government exams etc then go for BSc. If you want to learn the subject in details then go for BSc Hons or Major program.

Now for doing Msc its not always applicable that you have to pursue that subject only what you have taken in BSc Hons. For example, BSc Zoology are eligible for MSc Microbiology. So its not always true but obviously dependent on the subject of study. So if you specify that then we can provide you more customized answer.

I hope this answer helps. All the very best for your future endeavors!