Can I use Junk arm if the only trainer in my discard already is a junk arm?

[yeniths]

Say the only trainer in my discard is a junk arm, which was discarded through volkners early, can I use junk arm to discard two pokemon even if the only trainer in my discard is junk arm?

Also if i use junk arm can I use one of the trainers that I discared? assuming I can use junk arm in the first place

and last question, can I choose NOT to get a trainer using junk arm?

 

[PokePop]

You have to be able to get something,
So, while you can use the card if the only Trainer in your discard is a Junk Arm, you'd better be discarding another Trainer that you can get back or the entire play needs to be rewound.