Yes, this will fit a 10.5 inch barrel.
Yes the Hogue extension will work with this, the extensions will go in between the coupler/barrel nut and the rest of the forend.
While it will fit that upper, the installation is not a simple drop-in. This is a free floating handguard which means you would have to remove the gas block/front sight to be able to install this handguard to that upper.
That information is not provided by the manufacturer and you will need to reach out to them directly to verify. Here is their contact information:
https://www.hogueinc.com/contacts