Recruitment And Reservation Related Query

Hi, An advt. was published for the position of Assistant Prof. with a total of 5 vacancies distributed across 3 departments: D1 (1), D2 (2), and D3 (2). The reservations were allocated as: ST-Plain (1), ST-hill (1), UR (2), and OBC (1). However, these reservations were indicated as common across the departments rather than being specific to any one department. During the interview for the department: D1, 3 candidates appeared as follows: (a) A ST-Plain candidate with an age relaxation of 5 years. (b) A General category and a ST-Hill category candidate without taking any age relaxation. Questions: (1) Is it valid to specify reservations as common across the departments rather than being specific to any one department in the advt. as far as post based reservation is concerned? (2) Is it permissible to interview candidates from mixed categories as described above, i.e., candidates with and without age relaxation for a single vacancy? Thank you, Mrs Geet, Assam.