Single mommy in need of advice here!!

Okay so my son is 18 months old. We started to teach him very early why no meant and he responded very well to a firm no or a swat to the hand. But here we are at 18 months and he doesn’t listen to a single word I (or anyone on this planet for that matter) say to him. I could be talking to him and he will flat out ignore me. I will tell him no and he won’t even look my way and continue to do what he knows he isn’t supposed to be doing. Other times he will laugh and run when he knows he’s going to get a time out or diaper swat for doing certain stuff (I.E. climbing on our kitchen table, snatching the house phone and pressing a million buttons, taking the vent out of the floor and shoving his toys in it, opening every single cabinet, hitting, pulling the cats hair, throwing toys at my face, pulling hair, biting.) he is VERY SMART. Very. He can count to 5 he knows his colors and animals, trees, cars, he knows and recognizes a lot of letters, he’s just very smart. He KNOWS he’s not supposed to be doing these things but he just stopped listening to me one day and I don’t know what else to do. Nothing works, distracting him doesn’t work because he throws a massive screaming, hitting, and kicking fit on the floor.

WHAT DO I DO HELPPPP😭😭😭