Might you be able to get a little more specific? After all, "boyfriend" can mean about a million things. Exclusivity is also something where you'll need to be specific, especially in these times where -- hopefully, anyway -- no one following the guidelines is doing anything sexual in person with anyone else, or doing any in-person dating, in the first place.
Too, if what you mean by exclusive is that you're asking someone using Tinder or other similar apps to only talk to you and not to anyone else, I feel like your chance of a yes (or an honest yes) to that is slim to none. I say that because the whole point of using those apps is usually the ability to consider and talk to a wide range of people, and usually, if and when someone is moving to exclusivity with someone they met through them, it's because they have met in personal and then often progressed over time to an in-person relationship. By all means, you still get to ask whatever you want to ask someone, but I'm trying to manage your expectations a bit. It might also be worth talking about if, given what it sounds like you're looking for, dating/hookup apps + pandemic is even a sound way for you to go right now.
I do feel like if you're already not sure someone likes you for more than your body that asking for any kind of exclusivity might be putting the cart before the horse. Don't you want to know that *before* you make any kind of commitment with someone, rather than after?
Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it is the only thing that ever has. - Margaret Mead