Yes, you can seal a basement from the inside by installing an airtight sealant around the top of the walls and floor. This is usually done by applying a liquid membrane sealant that dries to form a tight, waterproof barrier. It's also important to caulk and seal any cracks or holes in the basement walls and floor, and to install adequate insulation in order to prevent moisture from entering the basement.

There is no one definitive answer to this question since it can depend on a variety of factors such as the type of basement, the climate/weather conditions, and what materials are used for the sealant. Generally speaking, most basements are not airtight and so it is difficult (although not impossible) to completely seal them from the inside. One option that may be worth considering is installing a vapor barrier on the inside of the basement walls and ceiling. This will help to reduce moisture infiltration and can help to make the basement more airtight.