Is the Flynama 28-inch good for daily commuting?

For short, flat rides on paved streets, yes. It has no suspension and basic parts, so long or hilly commutes will feel harsh and slow.

What size rider fits this bike?

The listing gives only a 28-inch wheel and a women's frame, with no frame size. Check the standover height and seat range with the seller before buying.

Does it come with a chain guard?

Yes. A chain guard is listed as included, which keeps chain grease off clothing.

Can I ride it on gravel or trails?

Not comfortably. The rigid frame, city tires and lack of suspension suit pavement, not gravel or dirt.

Does it need assembly?

Bikes at this level usually ship partly assembled. Expect to fit the front wheel, handlebars and pedals, and to check the brakes and gears before riding.