Just interested to know if an used auto can be stored for a long time . To keep as a spare.
The other thing is the weight of a auto , thinking it could be around 60 to 70 kgs

Would be best to store it somewhere that is air-conditioned all the time. Mainly to keep moisture from getting to it, plus the temperature would be stable.

Leave some fluid in it, doesnt need to be full, but not empty.
That'll get drained/replaced when you go to fit it.
Plug all the holes so moisture and debris cant get it, then wrap it in plastic. That industrial glad wrap stuff is best...
Store it somewhere dry, not on the ground.

Thanks for your replies .... Moisture would be the biggest killer . leaving the fluid in it and sealing it up with plastic wrap
l think perfect .

Im wondering how long you plan to store it? If its potentially a couple years then i think another threat is drying seals.
Leaving the ATF inside would help but it wont cover all the seals will it... as it would depend which way up its stored as to where the seals are actually located.

Not sure what the big drama is to be honest. Provided it has not been under water there is no need to plastic wrap it, store it in your lounge room with the air con going 24/7 or place it in a humidifier

We just take them out, clean them as usual after placing dummy drive shafts in them, dry them externally, re drain any residual fluid and also remove / drain the torque converter and place them on the shelf with all the other transmissions we have. They dont dry out, they dont tend to rust internally and they always perform as expected when placed back in the car. Some of the transmissions such as the Legnum ones can sit for a year or more and they go straight into cars, get filled and driven away.

I would suggest the plastic wrap more for the sake of keeping debris out rather than moisture.
Im making an assumption here that its probably going to be stored in a home garage/workshop?
So its likely to be a dusty environment? Maybe risk of wasps making a nest in some exposed pipes, Mice crawling in and around it? ect.
I know I clean my garage reasonably regularly and its still a dusty pigsty..