A Really Really Stupid Question

When playing around with roms on my nexus 7 I popped over to a 5.x one and it totally goofed up the file system and I had to wipe and start all over again. Wasn't that big of a deal since I back everything up off the device but makes it a bit of a pain going back and forth between 5.x and 4.x roms. Do the 5.x roms on the S3 do the same thing?

Help! I did something stupid.

I was using safestrap to try and install a custom rom, I wiped my stock rom but my phone ended up dying (I didn't see that the charger wasn't plugged in) now I can't do anything at all. IT just gets stuck on the samsung galaxy s5 logo. I cannot flash any AP I just get an auth failed error. I tried using the G900AUCU3BOC4_OneClick but I get an error on that as well. Please help me. I figured that I don't have an OS to boot into now. And I cant downgrade from 5.0 am I screwed?

Stupid phone won't take anything!

My S4 Active is soft bricked. Had 5.0.1 on it and wanted to SIM unlock it but I can't find a guide to do it. So since everything points to 4.x, I wanted to downgrade the phone. Well apparently that doesn't work because now the piece of junk won't boot up again. I can put it in download mode, but the stupid phone won't take anything. Odin keeps failing to transfer files to it. I have tried many 4.x builds, but with no luck. The phone turns on and complains that it needs Kies to fix it. Says "Firmware upgrade encountered an issue. Please select recovery mode in Kies & try again." Well I have tried that and even the stupid Kies software doesn't detect it. So how the heck do I fix this phone before I take a hammer to it?