Answer to "Have broken my screen . Where & how can I get it fixed?"The Fitbit screen is very delicate and needs to be protected carefully. You can shop for 0.2mm tempered glass screen protector to shield your Fitbit’s display against smudges, scratches, and stains. The tempered glass maintains the look of your device while safeguarding it from mishaps. Moreover, you will not be irritated by the air bubbles because of the latest technology.
Answer to "iPhone 6 and 6s Screens"The 6S has a few different features relating to touch usage as compared to 6. So I believe there will be differences in the replacement screen too. The display quality should remain the same though. Only the functionalities will be different. Have dealt with this query a few times while dealing with customers for my company, The Fone Stuff.
Answer to "iPhone 7 screen on iPhone 8?"I also own a mobile phone accessory company, The Fone Stuff. I have faced similar enquiries from some customers. I have to say it almost never works. The internal connectors are slightly different in the two phone models and even if you can somehow make the screen operational, it is going to face major lags. Hope this helps!