Is it Possible to upload Sketch file and filesystem together in the device to update or is it not possible ?
looking in platform.txt esptool.py appears to, I've not tried it.
When looking at the updater functions i would say it is, but i am not sure the IDE FS upload add-on actually supports it. When i ship devices with extra files in the SPIFFS i upload them once through the UART as i would also do for the initial sketch. I am sure i have tried but without success to upload the files in the data folder OTA.
Individual files i can always replace using an http file upload (of course this does also has to be implemented in the sketch)
I haven't found the need to truly investigate, and as said looking at the updater code, it should be possible to upload both the sketch and the filesystem OTA, mind you still as 2 separate steps.