is this considered HIIT?

i cruise down a hill on my bike, but go up it as fast as i can pumping my heart rate?

HIIT is medium-hard-medium-hard etc...

but now its like nothing-hard-nothing-hard

i will be using lowest gear (easiest to pedal) so i will be doing a lot of motion and my heart rate should be jumping off the ceiling

no, i do not believe your heart is going at its 90-100% downhill, as you can see, downhill, from my perspective, you probably exert little effort to pump the pedals...

try going uphill at your best (90-100%) for 45 seconds then go slow for 50-70% @ 1 minute
do this at a first gear. if u can. and repeat for up to 10 minutes.