does factory reset delete my gmail contacts, drive files, google plus photos e.t.c? I have a Note 4 and this is my first smartphone ever. So I'm illiterate about all these sync, backup, restore, reset stuff on smartphones. I setup the phone to sync all my contacts, google drive, google photos etc with my phone and it works fine. I even setup remote lock, locate my phone thing online. Now if I loose my phone or sell/give it to somebody else, I need to make sure I'll erase everything on my phone but keep all my data on gmail contacts, drive, photos untouched. I'm not using SD card.

If I do factory reset 


Do my gmail contacts, files in my drive, photos will be erased too or not?
Do I need to change my google password or my other accounts passwords after factory reset?
Wipe my device on findmymobile.samsung.com does it erase my online contacts, files in drive and photos?
Any data that is synced to your google account is safe. Factory Reset will only wipe data that is stored locally on your phone. Resetting your password won't hurt, but it's probably not necessary, especially if you use multifactor authentication.

Update

Ars Technica is reporting on a study that shows some information on some devices may remain after a factory reset. This could potentially include login credentials. For extra protection, it is recommended that you encrypt your device with a very secure password (more than 11 characters) prior to doing a factory reset. This will make recovery of that data less likely. I would add that many services allow you to revoke access from individual devices. For instance, devices may be removed from Google by going to security.google.com/settings/security/activity, selecting your old device and clicking remove.