I wasn't aware of that but it is still a rare version of the typical three-leaf clover.
No but they are much rarer than the common three leaf clover.
Is 7 considered lucky? 7? as in the number between 6 and 8? Correct.     A lot of people are superstitious about numbers. I'm not aware for 7 or numbers in general, I do understand that "superstition" means things like irrational actions or religious beliefs. Oh yeah I'm not religious about superstitions and such but I do believe in some of them like clovers. Clovers huh? Did you know a group of them is called a cluff? Interesting.     Four leaf clovers are not as rare as some think.
The four-leaf clover is a rare variation of the common three-leaf clover.