Hello, my friend. According to Apple Support, if you want to keep the RAW file format unchanged, you can directly import RAW images to an iPad with the Camera Connection Kit, and then turn on Download Originals. As for the trouble of whether the raw file changes format during the downloading and editing process, I can tell you that the Photos app uses a JPEG file as the original. If you want the photos to be kept in .raw file format, tell the Photos app to do so:
Step 1: In the Photos app on your iPad, double-click a photo to open it, then click Edit in the toolbar.
Step 2: Choose Image > Use RAW as Original.
If you're not sure whether the photos have changed file format or not, you can open the photos on a web site because most websites don't support a raw file. If the website fails to open them, then they're raw files.