Question: Are there situations in which a pilot could/has to lower the landing gear during flight for reasons not directly connected to landing? (i.e., not part of the landing checklist)

Originally I thought I had seen some around the location indicated by the pin on the map below (17° 25' 30.093" N, 78° 32' 27.4734" E), in the evening time around 4:00 and the weather was clear.

[![Sighting location](https://i.stack.imgur.com/78nOO.jpg)](https://i.stack.imgur.com/78nOO.jpg)

Answer: 
That's **nowhere near midflight**. You are seeing aircrafts approaching [Begumpet Airport (VOHY)](http://ourairports.com/airports/VOHY/)'s runway 27. This airport has no airline service, but it is used for some general aviation including VIP flights and as military airbase.

The point directly north (about 3 km) from the coordinates you gave ([N17° 25' 30", E78° 32' 27"](https://www.google.com/maps/place/17%C2%B025'30.0%22N+78%C2%B032'27.0%22E/@17.4532706,78.5342887,13z/data=!4m2!3m1!1s0x0:0x0)) is about 6 km, or 3.2 nm, from threshold of VOHY runway 27. Given usual 3° glide slope the aircraft would be just about 1000 ft above runway elevation, which happens to be the latest point where landing checklist should be complete. Yes, that means gear down. It also means it will be touching down in about a minute and a half.
Sure it's a private ***jet***? Plenty of single-engine piston powered aircraft have fixed landing gear.

Most jets cruise at high altitudes, so if you can a) see the aircraft, b) identify it as non-commercial, c) notice the landing gear is down, and d) claim that it's not near an airfield then it's more likely that it is a 4-6 seat piston single with fixed gear. Cessna, Piper, Beechcraft have made thousands.

Addendum to edited question:
You say there are no airports *near by*. Possible there's one a little further away? Planes typically raise the gear as soon as they are off the runway, but they lower it 30km out. And that's 30km flying distance, not driving diatance.