Google cardboard comes with 3D glasses. Does that mean that we will be able to watch 3D videos using a smartphone like the Moto-G (1st edition) which is not 3D enabled?
Google Cardboard is a Virtual Reality product which uses two images, one in each of your eye. Cardboard uses magnifying lenses in order to create a fake 3D image, your phone only splits as a display to both eyes. You need high resolution for VR, because the horizontal display is cut in half for each eye. I wouldn't use a Moto 1 at 720p, go for a Moto G3 with 1440p if you want decent results. Any Samsung models past the 4th generation (S4, Note 3) work good too.
To be fully Google Cardboard compliant, your phone needs to have gyroscope. If the gyroscope is not present, Google Play will report the phone as not compatible. If it is for watching side-by-side format 3d videos, we have a tiny ad-free utility app called iPlay SBS Player which does not need gyroscope.
No, not required. Instead you need applications made for Google Cardboard. It is a simple and an innovative idea from google. I have not tried it but had read and understood it in detail. You can find many applications from the below link. Also this works by splitting the screen of your normal phone, and presenting different views to each eye for creating 3D view.