Is it possible to develop for iOS10 and deploy to a personal iPad for testing without a developer account?
You don't need a developer account but you do need a Mac.  These points are taken from this blog:

In order to take advantage of this, you’ll need three things:


Xcode 7
iOS 9 (minimum)
A free Apple ID


To start, you’ll need to set up a provisioning profile to code sign your apps:


Open Xode preferences (Xcode > Preferences…)
Click the ‘Accounts’ tab
Login with your Apple ID (+ > Add Apple ID…)
Once you’ve successfully logged in, a new ‘Personal Team’ with the role ‘Free’ will appear beneath your Apple ID.




There's a few more details that you can view on that site.