@Shrisun, Q2A 1.8-beta1 version is out to be tested. You can download it on Github.
@Zeeshan, take a backup of your database then then just upload Q2A 1.8 files where you have Q2A 1.7.4 uploaded. Open your website then, initialize the database and you are done. Do remember that Q2A 1.8-beta1 may not be ready for production website (since it's in beta state only), so it's advised to use it on localhost or on demo site only.
