Yeah, UK.
And completely understand, this is truly the best way to learn, funnily enough this is pretty much how i started, i botched a modchip install (on a much older console) tried to resolve it…made it much worse, then left it, came back to it a year or so later having gained some much needed experience in both knowledge and practical skills and ultimately fixed what i though was unrepairable 
Thats good to hear, and one less potential issue. Yeah it’s useful, you can boot prior FW either through CFW or stock via hekate/SX boot menu regardless of fuse count so that’s good, though you may still have to generate another boot0 with EmmcHaccGen (or other) depending on if these were backed up without first doing a “clean up” in the SX boot menu, otherwise your boot0 backup will be the modified version and i am unsure if the modchip saves the original locally (which would likely be lost after modchip FW update) or if the modchip inteligently modifies the data on the fly, in which case it won’t matter. Regardless, you have all the important partition data backed up.