you 100% have 4 wheel abs, that's why you have 4 abs sensors, collapsing lines could be from age or contamination. I personally flush the brakes annually the fluid gets burnt and it's no longer up to spec, brake fluid is hydroscopic it absorbs water (reducing the boiling point), if not flushed it can ruin the whole system.All the info I have is listed. I’m not sure why the LF was not as hot the first time. I have a temp gun but it was not with me so I don’t know the exact numbers. The RR smelled hot but the LF definitely had that locked up caliper smell to it. I’m not sure if my Tahoe has 4 wheel ABS or not. I decoded all the RPO codes but none say anything about the ABS. I could smell hot brakes when I pulled into my garage and it was coming from the LF and RR when I got closer to them and smelled them. The RF and LR never had a hot smell or anything like that
brake fluid is normally clear looking not black.