Would filing bottom sides of two front teeth help reduce the gap in between two front teeth? (photos)

Filing(small amount of IPR) would allow closure of the space with additional round of aligners.  However, any filing will change the shape of your beautiful front teeth.  Depending on amount of filing, your teeth will begin to appear longer and narrower, not a good thing. I would suggest you look into some cosmetic bonding to correct the gap. This will correct the problem quickly and easily, at only a small cost.  You just need to make sure you find an experienced and skilled cosmetic dentist to perform this procedure, so that you get a great result and so that your gums remain healthy.  

you are partially correct. ipr of your lower front teeth will definitely allow for your upper front teeth to move backward. However, in order to do this properly you need to return to your orthodontist for an additional round of aligners

There are two ways to close this gap. The first is by reshaping the teeth and them moving them together orthodontically, possibly with Invisalign. The easier choice is to bond composite in the space to close it. Your dentist should be able to do this easily and without any tooth structure removal.