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I back up to my Google account and I use Dropbox too and My Samsung Account too with contacts also in my gmail. I save items to my Sd Card too.
There are a few ways to insure a mobile phone.
Some bank accounts also provide cover as a perk of the account.
Network provided cover and 3rd party options.
The answers yes to covering your phone if you wish via Vodafone.
Yes, you can use Google Drive, which will probably have enough space unless you have a lot of content. It may also take quite a long time, depending on your network upload speed. There are other options however:
1. Buy an sd card. You can then copy everything to this and transfer it to the new phone. Set it as default storage for as many apps as possible and things like photos and music should go there automatically. You'll never have to fiddle about with backup again.
2. Install a file manager app such the ES File Manager or File Manager from Cheetah Mobile (that's the one I use, but they're both good). You can then use it to access a shared drive on a PC (t logs in just like the PC itself) and back up to that. Note, btw, that 3rd party File Managers CAN'T write to an sd card due to Android security - you have to use the system one for that, but they don't access external networks.
3. Use the Transfer My Phone option which should be in you phone's main settings menu (as long as it's running Lollipop onwards). That'll pick up logs, SMS, contacts and quite a lot more, though how much depends on the manufacturer and whether the two phones are the same brand, I think.
Edited to add: you can't back SMS up directly to Google Drive. If the Transfer option isn't available, there are apps which will will back them up.
The only way to back up texts is to use a 3rd party app. The one to go for used to be called SMSBackup+, but I have a feeling it may have been renamed. I'm not sure what you mean by Tasks (though, if it's a To-Do list, use Google Tasks).
You can't duplicate files automatically on internal storage and the card other than by periodically copying. A better solution is to use cloud backup - Dropbox or Google Photos (or both). You can limit uploading to wifi only to save mobile data. Google Photos by default uses Hi Res rather than Original Quality, which doesn't count against your storage limit, so you don't need to do any housekeeping. Dropbox is best used as a vector for transferring to a PC. It only has a 2gb free limit, but preserves the files intact and uncompressed.
I got an sd card which has now all my pics and vids on it. Not sure why everyone doesn't go this way.
If you lose the phone having an external SD card doesn't help a lot. Photos should be uploaded to a cloud storage service and the best one is Google Photos. I use that even though I'm now an iPhone user. Microsoft OneDrive can do the same thing.
There are indeed downsides to using a card. They're slower (slightly), a little more prone to failure than internal storage and, as Jeff says, if you lose the phone, no help at all. That's why off-device backup is essential.
All that said, I do use a card, for the follwing reasons:
Ease of transfer
Recoverability if the phone itself fails - I'm not locked out of my content
I do use cloud and other backup, though.
They are almost the same thing. Photos is a subset of Drive. If you upload in high quality but not the full file size they offer unlimited storage.
You do need the Google Photos app to enable automatic backup, though. I use Dropbox as well as it preserves the full resolution (for trabsfer to a PC), but you do have to clear it out occasionally as the basic free allowance is only 2gb.
When you get your new phone, go into Settings and look for Transfer My Phone, which may be under Backup & Reset. You can use this to transfer content, including contacts, photos, music and SMS either via wifi or the cloud. Note that a lot of large files will (of course) take longer.
I've used it twice, though on both occasions it was to phones of the same make (which may enable more to be copied). It's a very handy utility and talks you through the process as you go.
When you log in to Google on the new phone, it will also offer the opportunity to restore from another device. That'll install all your apps and those settings that Google backs up. That used to include wifi passwords, but doesn't seem to now.
Much better to use OneDrive than Dropbox I would say. Open a Microsoft Live email account (Hotmail, Outlook.com etc) and you get 5 GB of OneDrive for nothing and the OneDrive app will backup full res photos just like Google Photos.
When you get your phone back, it'll have been reset and will be as it came out of the box, although it should have the latest available version of Android. When you sign in, tick the Restore box and your apps will be re-loaded and those settings that Google backs up will be restored. You'll need to re-do any changes you had to the default settings of 3rd party apps. Data for those apps will be lost. Any content you added yourself (music, photos etc) will be lost and you'll need to restore it from where it was backed up. You'll probably also need to sign in to wifi networks again, although the list may still be there.
You can restore apps manually, if you need to, by going into Google Play and looking at My Apps & Games. There are two tabs: Installed and All. Tap on All and you'll see the full list.
I don't use One Drive, but it's another possibility.