Transform an image into different aspect ratios

[SpaceMonkey]

Hello,

I just started today with this quest:

1.) Read the filename and save it.
2.) Resize the image to a specific aspect ratio.
3.) Add a prefix to the filename and save it as an jpeg in a specific folder.
4.) Undo all steps and repeat steps 2. und 3. different values.

I came this far:

Code:

from gimpfu import *

# The real code.
def setAspectRatios():
   # create the object of the image
   image=gimp.image_list()[0]
   # resizes the file to AR 2-3
   pdb.gimp_image_resize(image, 5333, 8000, -345, 0)
   # create the new name AR 2-3
   img_name_ar_2_3 = "AR_2-3_" + image.name
   # define drawable
   drw = image.layers[0]
   # save the image as jpeg
   pdb.file_jpeg_save(image, drw, img_name_ar_2_3, img_name_ar_2_3, 0.90, 0, 1, 1, "Aspect Ratio 2-3", 3, 1, 0, 2)

   
register(
   'set-aspect-ratios',                # Unique ID,
   'create different aspect ratios',   # Description/title
   'Add a white layer',                # Help
   "Author",                           # KJ
   "Author",                           # Copyright KJ
   "2024",                             # Copyright 2024
   'Set Aspect Ratios',                # The menu label
   "RGB*",                             # The type of images it can work on. Use "*" for all types
   # [                                 # List of input parameters
   #    (PF_IMAGE, "image", "Input image", None)  
   #                                                
   #],
   [],                                 # List of output parameters
   setAspectRatios,                      # The Python code that implementsthe plugin
   menu="<Image>/Layer",               # Where the menu label above appears
)

main()

But I have some questions to fill the blanks:

Q1: I know now that image.name does not work properly. Is there another way besides using pdb.gimp_image_get_filename(image) and trim the complete path down to the filename to just get the name of the file I imported?
Q2: What type is "drawable" - I could not find a good explanation. Do I use this correctly?
Q3: Undo is still a miracle for me. I saw that you can create groups and that you can enable, freeze, and disable it but I dont know how to trigger a simple undo to reverse steps 2. and 3. to the back to the original image.

Thanks in advance!