Hill repeat
 

How long should they be and how much climbing ft shoudl it have?

should it be a 3% grade or 6% grade?

i have a section im thinking of doing and its 200 ft of climbing in 1 mile.

whoever does hill repeats, what are your numbers?

gradient is meaningless, it depends on effort.

VO2 max intervals should be five minutes long at most, with equal amount of time "off" between sets

If you have a long-ass mountain road, then it's a FTP type, and you pace yourself accordingly (4x10, 3x15, 2x20, etc)

I do mine on a 0.5 mile hill with 260 of climbing.