Yes, this works. I use the disc as a Timemachine backup disc for several MacBooks (MacBook Pro 2016, MacBook Pro 2021, MacBook Air 2022). I formatted the disc with the native APFS. All you need is a USB-A - USB-C adapter to connect the supplied USB-A connector of the disc to the MacBooks. I see no reason why the disc should not also work with a MacBook Air 2019.

No, I can't. Aren't there special discs for Apple?

Unfortunately, I can't say anything about it.

The hard drive comes with a USB-A cable and the Mac Book Air 2019 has USB-C. So you need an adapter from USB-C to USB-A or a hard drive with a USB-C cable like the Seagate Ultra Touch HDD (5 TB)

Unfortunately, I can't say anything about it.