>>My question is, do I need Bootstrap for designing the page or it can be done simpler?
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>You never are required to use Bootstrap or any other framework - it's helpful, but certainly never necessary.
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>If you're building a simple single form application, using a framework like Bootstrap can be overkill especially if you're doing a mobile first Web page that is designed to primarily run on Mobile.
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>If you're doing simple data entry as you showed in your example, a few simple CSS styles can get you a nice looking page without having to load a big framework.
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>That said if you're building anything more complex it helps to use a CSS framework because it provides some base features that make it easier to lay things out consistently as well as handle the basics of Mobile vs. Desktop layout. This might be doubly true if you're not very good with HTML and CSS and if you have to do it from scratch on your own the result may not be very nice looking in that case whereas with a framework it will at least have the basic features of the framework :-)

What you are saying makes a lot of sense. Thank you!
I will create the page, first, without any styles, just ASP.NET controls. Make sure it works, as far as connecting to the SQL DB and updating it.
Then I will see if I can figure out what styles to apply (I am not good at styles, HTML, and CSS). If I can, the page will work and will be "light". Otherwise, Bootstrap to the rescue.