Rimuru Tempest gains Shizu's, Ifrit's, and the Orc Lord's powers by swallowing and killing them. Can he gain their abilities without killing them? Could he swallow someone without killing them, analyze their abilities and spit them back out alive? Could he analyze their abilities by touch instead? Thanks for your time!
Yes, he can gain abilities through various means.
When Rimuru swallows someone, based on the anime, their body is always destroyed but their spirit can survive. Even in the case on Veldora, when he's revived his body doesn't come out, only his spirit. Rimuru had to make him a new body.
If Rimuru wants to gain someone's full abilities, he'd have to destroy their body in the process of analyzing it and put their spirit in a new body has he did with Veldora.
Rimuru can attain a spirit's abilities without killing them as in the case of Ifrit. He also gained spatial movement through a spirit.
He can gain new abilities by swallowing the magic with gluttony. The adventurer's icicle lance is an example.
He analyzed anti-magic area in season two by touch alone to gain that ability.
In order to mimic a monster Rimuru would need to use predator to swallow a monsters body. But Rimuru can also swallow someone just to analyze them like in the case of Veldora he swallowed him so that Great Sage can analyze the barrier around Veldora in order to break it. But Rimuru has never copied a skill just by touching.