If I am creating new app, can I create it to work with backendless 3.x version? I don’t see any option on dashboard to change its version from default 4.0.8 to 3.x.
The 3.x version is available for apps only on the paid plans. Could you please clarify why you specifically need that version rather than the latest one (4.0)?
Because I am trying to integrate open source chat sdk in my android app. Its documentation mentions - “Make sure that Backendless 3 is selected from the Backendless dashboard.” and I am unable to find this option on backendless.
That option has been disabled. If you absolutely need an app in the 3.x version it might be possible, but you would need to be on the paid plan (only Cloud9 and Cloud99 plans are available in 3.x). Please contact firstname.lastname@example.org to get more information.