PoStat4evr, your first, from Secunderabad/Deccan is fairly simply explained. Secunderabad was the town; Deccan was the region - essentially, Hyderabad State.
Secunderabad was a major cantonment, or military base in modern terms, in Hyderabad State, and quite close to Hyderabad Town. Not
postal stationery, but a delightful cover nonetheless:
from Montgomery's Hotel at Secunderabad. Apparently it was one of the two hotels one could stay at when in Secunderabad.
And as a footnote to a footnote ... Secunderabad derives its name ultimately from Alexander the Great. He never made it as far as Hyderabad of course, but his fame - or notoriety - spread throughout the Middle East.