Short answers, pulled from the story.
Tappi Iwase, sometimes credited as TAPPY, is a Japanese musical composer best known for his work on the Metal Gear and Suikoden franchises. He composed almost all of the score for Metal Gear Solid, with his main theme carrying forward into Metal Gear Solid 2: Sons of Liberty and Metal Gear Solid 3: Snake Eater.
Tappi Iwase studied music with Dick Grove at the Grove School of Music, which closed in 1991.
Iwase's main theme was discontinued from Metal Gear Solid 4: Guns of the Patriots onward due to allegations that its melodies were plagiarized from a classical piece by Russian composer Georgy Sviridov.
The ending theme "The Best Is Yet to Come" for Metal Gear Solid was not composed by Tappi Iwase. The music for the game's cinematic scenes was composed by Gigi Meroni, while Iwase handled the rest of the score.
Iwase's main theme originated in Metal Gear Solid and arrangements of it were subsequently used in Metal Gear Solid 2: Sons of Liberty and Metal Gear Solid 3: Snake Eater. It was dropped starting with Metal Gear Solid 4: Guns of the Patriots.
Georgy Sviridov was a Russian classical composer whose work was allegedly the source for melodies in Iwase's Metal Gear Solid main theme. The plagiarism allegation led to the theme being retired from the Metal Gear franchise beginning with the fourth mainline entry.