The way that Apple handles notes on the iOS devices is that really they are just specially formatted email messages being sent to yourself from yourself. This was a bit more obvious in earlier versions of OS X as the notes you would write would appear in the apple email client Mail.app.
If you want to use you iCloud account to sync your notes then yes apple forces you to create a free iCloud.com (used to be me.com) email address which is really not a bad idea, but for someone who already has a gmail account it certainly is not necessary.
if you would rather have your notes sync by way of your gmail account you will need to open the settings app on you iOS device(s) then tap on "mail, contacts, calendars" and add your gmail account there. You will then have the option to turn on or off several services like email, contacts, calendars, and notes. in fact you can turn on nothing but notes should you desire.
it wil also be a good idea to visit Settings > Notes on your iOS devices and choose the account you wish to be your default note creation account to avoid any future confusion.
If you are setting up notes on an OS X computer and need help try using this online guide that apple provides. it covers how to set up mail and other services on a number of different systems.
http://www.apple.com/support/macosx/mailassistant/
You have multiple questions here, so one answer at the time:
When your iPhone is connected to a Wi-Fi network, any app that needs data from the Internet will use the Wi-Fi network instead of the cellular data network. The data usage is therefore not counted against your monthly cellular data limit. However, when not connected to a Wi-Fi network, any time an app needs data, it uses the cellular data network and is counted towards your monthly limit.
Stopping apps from using Cellular Internet data:
That can be done in your iPhone settings. Select Cellular and it will open new window showing who and how much. There is a slider to turn that app off from Internet data.
At the bottom of the list, there is an item named System Services. Selecting it will show how much cellular data is being used for things like Messaging Services, Push Notifications, Documents & Sync, iTunes Accounts, Siri, Voicemail, Software Updates, Find My iPhone, Diagnostics and Apple ID Services.
Remember those are cumulative data, so rest them once a month in date accordance to your plan.
There are few external apps for measuring and controlling internet data.
For Safari and FireFox, go to the individual settings and disable the FlashPlayer to prevent sites loading unwonted flash based advertisements. You will be asked to enable it if you do want to watch something.
Best Answer
To rotate a photo on an iPhone and share it with Whatsapp:
Editbutton on the top-right (note: if you're running the iOS 10 Beta, you'll need to hit the slider button on the bottom toolbar)DonebuttonWhatsappin the list of apps you can share the photo to, scroll all the way to the end of the app list to the more button, hit the more button, and turnWhatsappon.Let me know if this helps!