SQL Server Multiple Installations? I have been using SQL Server 2012 on my laptop, but now I want to install SQL Server 2014 trial version as I am following an online course on it.

Can I go ahead with the installation of SQL Server 2014 trial with SQL Server Data Tools installation separately?  Is it advisable to do that or will it create issues and errors if I try to do so?
You should have no problem running multiple versions of SQL Server on the same box.  By default, they will install into separate folders, and won't interfere with each other.

Having said that, I wouldn't bother with the trial version; just use the free Developer Edition assuming you're not using production data.