How do you get a shield in sonic 3 and knuckles

It's been a while since I've played this, but I'll give this a shot:

1. Playing as Sonic, collect the 7 Chaos Emeralds (to get a Chaos Emerald, find the large gold ring hidden in one of the acts. You'll be warped to the secret stage, where you'll have to collect all the blue spheres and avoid the red ones. Once you do this, you'll be given a Chaos Emerald! Only 6 more to go!)
2. Once you do have all 7 Chaos Emeralds, collect 50 small rings.
3. Once you have them, press the jump button twice.
4. Instead of using the split-second shield, Sonic will transform into Super Sonic.