Any drawback in using AWS RDS "dev/test" instance for production?

There is no persistent difference between choosing the Development and Production options in the new RDS instance wizard. Selecting the options simply chooses different defaults on the following pages:

Production:

• Instance Class: db.m3.xlarge
• Multi-AZ: Yes
• Storage Type: SSD
• Allocated Storage: 100 GB

Development:

• Instance Class: None selected
• Multi-AZ: None selected
• Storage Type: None selected
• Allocated Storage: 5 GB

If you selected "Development" in the first page, then change the default options to the "Production" options, then you have a "Production" server.

If you selected "Production" in the first page, then change the default options, you can run under the free tier.