If your 2 year old is regressing during potty training then they likely are not ready to potty train.
Some parents think that just because a toddler is going to the potty with their help they are potty trained when in fact and in reality it's the parents that are potty trained and trained to take the toddler to the toilet.
Just because a toddler can pee or poop on the potty it does not mean they are ready to be out of diapers and be potty trained.
I don't actually myself believe in potty training and when a kid is ready to use the toilet they will use the toilet.
If you have to constantly run the toddler to the toilet every 30 minutes or so then they are not ready.
I would rather change diapers than run the child to the toilet that often.
My mom told me she potty trained me at 18 months old but she said she had to help me pull down my pants, pull up my pants, wipe my bottom etc and would have to take me to the toilet or I would pee my pants.
So in fact I was not potty trained then and would wet my training pants or diaper without her taking me to the toilet.
Some kids are not ready to potty train until 3 to 4 years of age.
My youngest son didn't potty train until he was near 5 years old and then one day he decided to just use the toilet and didn't want a diaper anymore.
They will get it when they get it.
My 3 year old boy right now is still in diapers and I'm not gonna even try potty training him as he will stop wearing diapers when he decides too.
Diapers are just another type of underwear that happens to be absorbent.
No shame and no age limit in wearing diapers.