We are getting new windows. The old windows has this film. The film is less than a year old. Can we reuse this film?

Sadly only the static cling films are reusable. I see the question came in on the reflect protect page, so if this is the film, then it's adhesive backed. They are clean removal, but not technically reusable. The adhesive layer will stretch a bit during the removal process so if you try to reinstall, it might not look very good.