I first added GMIC to gimp at least over a year or 2 ago, and I'm thinking I should probably update it. What's the best way for me to do this?

Also, what does the Transparent difference filter do? I cant seem to get it to do anything, but based on the name and the sliders and drop downs, I think it may do what I was/am trying to do as described in the topic I made on /r/gimp titled "APNG/LCF extension and Layer mode/Alpha question" (I can't post urls since i'm a new user so sorry)

If it indeed does that, is there a way for me to automate this? Specify a base background layer, and then have the filter applies to every other layer in the image using the specified background as the source?

If not, is there a filter in GMIC that does this?

Major releases have to be manually updated unfortunately. Once you copy the latest gmic plugin into your plugins folder, you then can update the presets using the update button.