No
No hyphen is needed for world class. World is just an adjective that describes class much like (for example) upper class, which also does not need a hyphen.
There are specialized directories listing Yoga Studios around the world. You will need to look for an instructor that meets your needs. For example, instructor's experience, location of the class, class timings, reviews on the studio etc. One of the Yoga directories is listed below.
It does not need to have a hyphen! :)
pilates and yoga help!! x
Yes, one is said to be enrolled in a yoga class.
Yes, in this case "seventh-grade class" should have a hyphen to show that the words "seventh" and "grade" are functioning as a single adjective modifying the noun "class."
No, the word "nineteen" does not need a hyphen when written numerically.
You don't necessarily need yoga pants, but it would probably help. You can purchase a very cheap pair at Old Navy, if you don't live near one you can check www.oldnavy.com.
No
Runner's can improve strength if they do yoga. It increases flexibility as well as balance which benefits any athlete or runner. Beginner yoga class is best before going to advanced class.
It's not a word in the dictionary, so yes, use the hyphen.
I do not believe that multitasking is supposed to have a hyphen.