Use of multiple Master Pages in Asp.net

Yes, we can. You can specify the Master Page, your page will use at the time of adding a new page to your application. If you want to change the Master Page at run time, you can use the following statement to change it with below statement.

this.MasterPageFile = "MasterPageName.Master";

However, ensure the placeholder controls placed on the master page you're using matches with your Content page.

Yes and this is the way by which you can use more than one Master Page in the Web Application.
Hope it will help.