There is an installation guide: https://images.homedepot-static.com/catalog/pdfImages/19/19270580-5cdf-424a-9af8-abdf204d8899.pdf which you may have already seen. It refers to Electrolux products, but apparently it covers this one.
Yes it is. See the listing at Lowe's: "Item # 1339555 Model # FGMO226NUF Frigidaire Gallery 2.2-cu ft Microwave with Sensor Cooking Controls (Smudge-proof Stainless Steel)"
I asked the same question (about the width) and Frigidaire says the minimum width is 24 3/4 inches and the maximum is 25 inches. The installation guide refers to an Electrolux product that presumably is the same as this. I noticed that many of the reviewers noted difficulties with installation.
This trim does not come with a bracket.
It's model compatibility is FGMO226NSS.
The 30" will not work, at least that's what the specs (verified by Frigidaire) say, because the maximum width is only 25 inches (the minimum width is only 1/4 inch less) and because the 27" refers to the outside width, that won't work either. So to use one of these products, you'd have to alter the width of your cutout. The height is even a harder problem for the 30-inch, because the minimum is 16 inches. Here's a summary of the specs from the installation guide, which, confusingly, refers to Electrolux instead of Frigidaire: Height Minimum 16 3/4" (42.5 cm) Maximum 17" (43.2 cm) Width Minimum 24 3/4" (62.9 cm) Maximum 25" (63.5 cm) Depth Minimum 20" (50.8 cm) You might check the minimum height in the specs for the 27" model if you want to narrow your cutout width to match its requirements. Of course some of your work would be visible if you narrowed a 28.5-inch width and covered it with 27"-wide trim.