2nd Regt were the Queens Royal Regt of Foot until 1881, then the name changed to the Queens Royal West Surrey Regthttp://www.regiments.org/regiments/uk/inf/002WSurr.htm
The regiment had 2 regular battalions at the time, so he could have been in either:http://www.regiments.org/deploy/uk/reg-inf/002-1.htmhttp://www.regiments.org/deploy/uk/reg-inf/002-2.htm
Since you have him in Devon in 1865 I'd say 1st Btn was the more likely.
Can you give us his name? Could try a few lookups for you.