GE Sealants & Adhesives Max* Shield All Weather Sealant, 10.1oz

I'm confused. The product description says it fills 3-inch gaps, yet the instructions say you need a backer rod for gaps over 1/2-inch. Which is it?

Can I use this in my shower to seal the the grout line between linear floor drain and tile? Is it durable to scrubbing?

Will it hold up for years in the sun?

Can I use this to seal gaps in woodedn floorboards inside my house?