case II- yes, you are fully eligible for break journey at agar because ngp to agra is more than 500 km. actually case I and case II are just the same. the only difference is in case I u r nt booking onward as u r nt sure when and which train u ll catch and in case II u r sure of ur onward journey and hence plan ur b/j or o/j accordingly by booking at prs. in both cases, resvn charges is to be paid...either to tte/to the prs. same fares for both cases.
if u continue within 24 hrs of arrival of 1st train, no resvn charges to tte/prs, if later, fresh resvn charges is the only difference.