Are a flight instructor certificate and commercial/airline transport pilot certificate printed on the same physical piece of plastic, or on two different ones?
I can’t speak for other countries, but in the United States, a flight instructor certificate is a separate document from a pilot certificate. Flight instructor is not a rating which is applied to a pilot certificate. It is an individual laurel with its own privileges and responsibilities separate from a pilot certificate.
While my flight instructor certificate is similar in form factor and coloring to my pilot certificate, it is a different document. The back of it states that the certificate is not valid, unless accompanied by a pilot certificate No. 12345678 and that the document expires 31 August 2024.
It also contains limitations, such as Airplane Single Engine and Airplane Multi-Engine and privileges such as Instrument Airplane.
Other countries may vary from the United States, which is where my certificate(s) are from.