Lala-1 – A research prototype with an open-frame rear fuselage, twin tail and twin tailwheels supported by struts under the rear of the fuselage pod. An Ivchenko AI-25 turbofan engine was fitted in the rear of the fuselage pod for use as a development model for the WSK-Mielec M-15 Belphegor agricultural aircraft.[4]
An-2F – Developed concurrently with the An-2 prototype, 'Izdeliye F' was an experimental artillery-observation aircraft with a twin-tail, ventral observer's position and dorsal defensive machine-gun position. The initial service designation of An-2NAK was changed to An-2F once post test flight modifications had been carried out. Two prototypes were built, with the first completed in the summer of 1948, but flight testing was delayed to April 1949 due to the need to incorporate modifications called up from the standard An-2 flight test programme. The flight test of the An-2F showed that the aircraft met all the requirements of the specification, but helicopters were demonstrating that they could perform the artillery correction role without the need to provide fixed base airstrip for them to operate from, thus the An-2F was not proceeded with and the two prototypes were retained by the Antonov bureau for hack duties with one later serving as a flying wind tunnel to investigate para-dropping from the Antonov An-8 twin-turboprop transport.[4]


I saw these AN-2's being developed, & I thought of you!
That could complete our AN-2 collection? I did not realise how many different versions there were.

PS Theres also an AN-2 100 & an AN-3, a turbo prop version.. and a LOT more on wiki.
https://en.wikipedia.org/wiki/Antonov_An-2