Will Hydroquinone 2% be able to lighten flattened moles on my face?

2% hydroquinone is a good starting place.  The prescription level in the US is a 4% HQ, and your doctor can have a compounding pharmacy create a higher dose, like a 6% or 8% if needed.  I find that people who do not respond to the HQ usually just need a higher dose.  Don't use it long term--it is best to cycle it if you need to use for more than 2 or 3 months.
As an aside, get the moles checked out before you start lightening them and changing their color.  You don't want to inadvertently treat a skin cancer and delay its diagnosis.
Best of luck to you,
Dr. Amy