The man given most credit for introducing the extended dolphin kick in backstroke was David Berkoff and it was known as the Berkoff blastoff.
The commentator's attempt at Daichi Suzuki's first name is typically terrible.
The 15-meter rule was introduced to avoid races being swum mainly under the water.
The proper name for the stroke swum on the belly is crawl, variously known as front crawl (the usual term in Britain) and probably depending on nationality the Australian crawl or the American crawl. Johnny Weissmuller's famous book is called Swimming the American Crawl and is well worth a read if you can find a copy. The race is the Freestyle race and in principle you can swim any stroke you like and people often swim backstroke, butterfly or breaststroke in masters competitions, but in the Olympics (apart from the first few when some swam Trudgen) that has probably never happened because the crawl is the fastest stroke.
The original backstroke (or at least one of the original styles) was swum with both arms and a breaststroke kick and is known in Britain as the Old English Backstroke, but people soon found that an alternating action with a flutter kick was faster and so it came to be known as the back crawl or nowadays just backstroke, but the Old English lives on in masters swimming and some are faster with it than with back crawl.
There's a chap from Brazil on youtube who thinks he has invented a new stroke, but it's just Old English. I wrote to him to tell him that it has been described in many early books on swimming but he seems to prefer to think that it's all his own.