You can, but it's not a lot of fun. I did it for years as a modified BBB element in 5/3/1. I have, at various times done 5x5 squat past 4 plates as well. Didn't last more then 3 weeks before I had to back off, I'm too old to recover from that, but I was working Texas Method at 415 lbs, which was just as hard as it sounds.

Sure you can, it's just that progress goes much slower. When I finally got into the 500s I was counting 1/2 and 1/4 reps as progress. For example, if I got 525 for 3-1/4 reps for one workout, and later got 3-1/2 reps, that was progress. Keep in mind for me that later could be weeks or months as I'm not naturally big.