I use a non-disposable 35mm camera like kodak m38, and the film I used is kodak ultramax 400. This is my first time shooting films, I would really appreciate any help given. Thank you.
The only difference between the 24 exposures promised on the box and the 27 exposures you were able to take is the difference between how much of the roll was pulled out of the film cannister and exposed to light during loading your Kodak M38, and thus how much of the film was still inside the film cannister when the back of the camera was closed, versus how much film needs to be pulled out of the film cannister to load other cameras like older 35mm interchangeable lens SLR cameras.
Although roll film is marketed to take a certain number of shots, roll film has no frames until it is exposed. It's just one long continuous piece of unexposed film.
The frames are created by the width of the camera's film gate. The film gate is the hole just in front of the film that determines how much of the film is exposed each time you take a photo. Only the part of the film directly behind the hole will be exposed.
The gap between each frame is determined by how far the camera advances the film before it will let you take another photo. For most "35mm" cameras which actually use 135 format film, the film gate is 36mm wide, 24mm tall, and the film advances 38mm (which is equal to exactly eight sprocket holes on the edges) for the next photo, leaving a gap of 2mm between each frame. 135 format film is actually 35mm tall (that's where the nickname "35mm" comes from), but the extra 9mm, split between the top and bottom that are above and below the 24mm height in the middle that is actually exposed, are used for the sprocket holes and for printing film type, batch information, and frame numbers by exposing just the margins when the film is manufactured.
This piece of 135 format film has already been (over) exposed and developed, then five frames were cut from a longer strip. Prints from this film would be almost totally white. If it had been developed without first having been exposed, the entire 24mm tall middle would be the same light color as the unexposed 2mm gaps between each frame, and prints from such a negative would be almost totally black.
Older 35mm cameras required more of the film be pulled from the cannister when loading. One needed enough film to insert the leader into a slot in the skinny spindle of the takeup spool. Newer 35mm cameras made near the end of the 20th Century, especially those called "compact" or "point and shoot" 35mm cameras, which usually had a lens permanently attached, often required less of the film to be pulled from the film cannister to load the film and close the back of the camera. Often the film cannister sat closer to the edge of the film gate, as did the takeup spool or takeup roller on the other side of the film gate. Instead of a takeup spool with a skinny slotted spindle in the middle, many of these "compacts" have motorized rubber rollers that apply enough pressure to the sides of the film to insure it winds onto the takeup spool or roller. Even SLR cameras with interchangeable lenses that had a motor automatically wind and rewind the film also often wasted less of the film during loading. I often got 26 and sometimes 27 frames from a "24" roll of film with my Konica FS-1 and later almost always got 27 with my EOS Rebel SII. Both were interchangeable lens film SLR cameras with motorized film advance.
At one time some film brands began marketing their "24 exposure" rolls as "24+3" or "27" rolls. In Japan some still label them as "27 exposures".
The only difference between a 24 shot roll of 135 film and a 27 shot roll of 135 is the labeling. They're the same length. It was just that the newer self winding cameras that came along in the 1980s and 1990s could get more exposures from the same film length. During the transitional period when many users still used manually wound cameras but the newer self-winders were becoming widespread such rolls were sometimes marketed as "24+3" rolls. The older traditional cameras that required spooling the leader through a slit in the middle of the takeup spool could only get 24-25 shots out of the same roll that a self-winder could get 27.
Here is where the "extra shots' come from:
"24" rolls only need 910mm± of length to fit 24 frames that are each 36mm wide plus leave 23 2mm gaps between those 24 frames. But Kodak's 135 format "24" rolls are actually 1130mm± long. The extra 220mm± length allows for the amount exposed to light that is needed during loading the film into 135 format cameras that need the most pulled out of the cannister when loading the film. It also allows for the length left between the other end of the film that is attached to the spindle inside the film cartridge and the position of the final exposure.
If I develop it, will it become a blank roll?
Once the film is developed the development can not be undone. It is chemically "fixed" during the development process. "Fixed" in this case means no longer chemically reactive to additional light. It's more or less set in stone.
If the film was never loaded into your camera properly and never advanced out of the film cannister, then none of it was exposed. But once an unexposed roll has been developed, you can't then put it back in your camera and expose it because it has been "fixed" as a blank piece of film and will no longer chemically react to light.
The fact that you got 27 frames, which is about what one would expect from a "24 exposure" roll when using a compact 35mm camera like your Kodak M38, is a pretty good clue that you did load the film correctly and that you did actually expose 27 frames before the film ran out.
Have it developed and see what you captured!
A roll of film is one big long strip of photosensitive material. The frames are not marked out in advance. The 24 on the box is a (usually accurate) estimate of how many photos you will be able to take. Depending on your camera and how you load the film, it's not unusual for the strip to provide you with one or two (or more) exposures more than you were expecting. You can think of them as bonus free exposures. There's no problem here for you to worry about.
Enjoy film photography!
It might be that you did not link the leading edge of the film into the takeup spool properly, meaning the film may not have advanced for any of your exposures or the camera was never loaded.
You may have moved the film advance lever a little too hard and the end of the roll is still taped inside the canister but you have torn the sprocket holes in the side of the film.
Or you may have pulled too hard and tore the film from the canister and all of it is on the winder.
Sit inside a closet in a dark as possible room; at night is best. Sit for some time to allow your eyes to adjust to the darkness and if you can see ANY light, it will "fog" your film. If you are in total darkness, open the back of the camera and feel if the film is still stretched across the shutter. If yes, close the camera and rewind the film. If you can feel all film is onto the takeup winder and not connected to the canister, shut the camera and arrange for the developing lab to remove the film using a black changing bag. It is like a sweater inside another sweater, with elastic on the sleeves and the waistline is double zippered. The lab technician puts the camera and a light-proof film container or reloadable film cassette inside the inner bag and double zips it closed. S/he puts their arms inside the sleeves and opens the camera and transfers the film to the container, seals it, and removes everything. https://lensnotes.com/photography/film-changing-bag/