Popsaka, that is pure MkVb, apart from the barely visible tailhook, and the four-blade airscrew. The oil coolers are the correct asymmetrical type, and it has the short nose of the 40-series Merlin. Don't be fooled by the six-stack exhaust stubs as these were often retrofitted to MkVs.
The MkIX had symmetrical coolers, a longer nose to house the 60-series Merlin with six-stack exhausts, and a fixed tailwheel. Early MkIXs were often rebuilds of MkV or even MkI/II airframes, so initially, those were the only significant differences. Various cowlings were used, again, some being made with lengthened parts from the MkV. Further mods involved the broad chord rudder introduced on the MkVIII, and new elevators. Most MkIXs had the C or E type wing; despite rumours, none had the A type, although a very tiny number of early machines may have had the B type.
The MkVIII has the above features, but with a retractable tailwheel and pointed, broad chord rudder. Internally, the fuselage was reinforced and therefore stronger. All MkVIII aircraft had the C type wing. MkVIIIc aircraft were deployed in the Med and Far East only.
The final Merlin-engined variant to see service was the MkXVI; these were externally identical to late-build MkIXs, and differed only in that they were fitted with the American-built Packard Merlin. These aircraft all had the E type wing.
No Mark number at the time differenciated between the full fuselage and the cut-down fuselage types. The cut-down fuselage could be fitted indifferently to the MkIXe and MkXVIe without the aircraft's designation changing. Later Griffon-engined models did make the difference, as in the Mk21 (full) and the Mk22 (cut-down).
Seafires were a basterd (the word appears to be forbidden by those who forbid such words!) mixture of "off the shelf" parts all assembled according to FAA recipes. The first true naval Spitfire derivative was the MkIII, which introduced the folding wing. It gets a bit complicated... But the Seafire MkI was only a Spit MkV which belonged to the Navy, and the MkII was a mildly modified MkV, as shown above.