1. This is definitely not an option for safe long-term storage and will cause damage. Lying down or hung up is best.
Sitting for an extended period of time can cause compression marks where the legs are bent and she may develop a flat butt.
If it’s only 2-3 days it should go away after they are moved back to a standing position for a while. It would be better to have her standing and leaning against the wall with a soft towel or blanket between her back and the wall.
2. Personally, I would only leave a TPE doll in that position for a matter of hours, the long-term issue will be tiny cracks forming in the groin area because the TPE has been left in a stretched position for too long. If your doll has standing feet, then having her stand while gently leaning against a wall would be far better. After a few years, those pesky micro-cracks will begin to appear in the groin in any case after the legs have been moved up 90 degrees but leaving her sitting will speed the process considerably.
3. The only one of my dolls I will leave sitting for any length of time is my silicone Sino and she sits on a soft chair with a pillow between her bum and the seat, but she gets regular lying down breaks when she can stretch out.
The TPE girls either laze around in bed or stand leaning against the wall with a memory pillow between their backs and the wall. Do NOT leave her leaning against a wall wearing anything dark – recipe for staining! It is also a good idea to put socks and trainers on her to protect her feet (and your floor covering from the standing bolts, which should be allowed to protrude a bit to protect the soles of her feet).
4. I highly recommend alternating between sitting and lying down, but yes, standing, leaning against the third point of contact with the legs completely straight, knees locked and legs slightly spread apart (shoulder width) with something between the wall and the dolls back to prevent oil stains on the wall is the best option.
