Misc: name of the highest volcano in the world?

Questions

80's - Who sang 'Head To Toe'?

80's - Who sang 'Shakedown'?

80's - How many No. 1 songs were on Michael Jackson's 'Thriller' album?

80's - What was the title of Poison's only No. 1 hit?

80's - What is the name of the disgraced duet that had three consecutive No. 1 songs in 1989 before surrendering their Grammy Award?