Use bundle with bootstrap 4 inside webforms project with bootstrap 3

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WebForms

bootstrap

ReactJS

I have a webforms old project using bootstrap 3 and i´m starting to build new implementantios with React JS.
I create a bundle.js (a transpilation of my main index of the React pages folder) and execute this bundle in a WebForm page:

<asp:Content ID="Content1" ContentPlaceHolderID="MainContent" runat="server">
    <section >
        <div id="app">
        </div>
    </section>
</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="PageScripts" runat="server">
    <script src="React/dist/bundle.js" type="text/javascript"></script>
</asp:Content>

The problems is: My React´s scripts are using Bootstrap 4 and when they´re renderized, it happens some conflits between the two versions of bootstrap.

Anyone has an idea of how could i isolated a div or a page only with the version 4 and keep the 3 for the old pages?

What I have tried:

I´ve tried using SASS and LESS styles to create a CSS tag to apply the version 4 only for a div, but with no success.

<section class="bootstrap-iso">
      <div id="app">

      </div>
  </section>

And the scss style:

.bootstrap-iso {
    @import url("https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.min.css");
}