Kelly won tickets via a radio station contest to see George Michael. The episode aired in October of 1989 and presumably took place in 1989. In 1989 the U.S leg of George Michael's Faith tour had ended (it ended in 1988) and the only dates left on the tour were three dates in Spain. A local radio station in California would only be likely to be giving away tickets for a concert in California, but the California dates of George Michael's Faith tour took place in October of 1988, not 1989.
Screech didn't want to go to the beach with Kelly because he has a fear of sand. But he didn't have a problem going to the beach in the season 3 episode "Cut Day" and worked at the Malibu Sands Beach Club in that same season.