Toyota RAV4 Oil Type

I Recently Was Scheduled For An Oil Change, And Appr. 1.5 Weeks Before, I Checked The Oil And It Was Down By 1 Quart. I Raised My Concern...

What Kind Of (brand/kind/gauge) Engine Oil Should I Use For My Vehicle Listed Above? Thank You.

Can I Dump The Engine Oil Out And Put It Back In? (because I Put Too Much, Oil And I Did Not Have The Oil Filter Remover So I Did Not Change...

How Much Oil And Viscocity Type Is Needed For A Regular/routine Oil Change In A Temperate Region Like Nigeria? Mechanics Say Just One Gal....