Reddit mentions of Toddler Sleeveless Bodysuit 2T, 3T, 4T, thru 14/16

Is your daughter in aba therapy? I would definitely ask her therapist if she has any ideas or witness this kind of behavior before and see what she recommends.

For clothing, I suggest getting bodysuits for your daughter that have snap enclosures at the bottom:

https://www.amazon.com/Toddler-Sleeveless-Bodysuit-8-10-10-12/dp/B0087PZ7DA

They are much harder to open and as you can see from the reviews is popular for older special needs kids. Another idea would be to get rompers that have buttons on the front or back in order take off like:

https://www.amazon.com/gp/product/B06XHL2F3C/

Do avoid spaghetti straps or anything with large necklines cause those are easy to wiggle out of.

If your daugther likes tight fitting clothes, weighted blankets/vests, etc. You can also try a gymnastics unitard out.

For the pottying aspect, I suggest getting portable potties for every room she spends times in so you and her have fast easy access to plop her down when she needs to go. I suggest sitting her on the potty every hour while awake and every 3-4 when asleep. This can be tweaked based on what you think her pottying habits are, but its a good baseline to start at and time can be slowly incremented once you get a good feel for her toileting times. It helps to keep meals and snack time to be around the same times.

Whenever you sit her down on her potty use sign language, pecs, vocalizaton, whatever you think she will catch on first and be consistent. Let her sit for 5-10 mins than continue throughout your day. When she does potty, make a big deal out of it with whatever motivates her might be singing a song, few m&m's, her favorite youtube video, whatever you decide to use make sure you use it exclusively for a successful potty.

You're right that she see no benefit for her to potty successfully, so that's why you need to create one for her to see and kids with autism it's harder for them to connect the dots, so it's important you are consistent.

It's also okay to take a step back on trying to potty train if you don't think she is developmentally ready and just focus on trying to keep her diaper on.