Ciao I-2021, as I thought the Red Light
Extinguished
....
- landing gear is down and locked with landing gear lever DN.
is not very popular.
But it is an official information, why not take advantage of it if short of fuel or any other stressful situation...
Btw, recicling the gear is NOT recommended by the Training Manual, and you lower the gear at latest with Flaps 5, not 15.
In your scenario, you already have Flaps 15, so no need to raise the gear to make sure the horn is working.
You will already get the warning horn with F15 if one leg is not extended.