1. They Probably do not let you delete legacy forms because legacy forms are used in mobile. Currently new forms do not rendering mobile but hopefully that will change in the third or fourth quarter where new forms are supposed to work on mobile.
2. It's not a way to make a form read only. A better suggestion if possible is to use custom permission rules to have the record being non-editable two users in certain rules under certain conditions. That way the record itself will not be editable.
3. Ben Simon, our Community Forum moderator, is working hard behind the scenes to get all the bugs out of this new Forum platform. He is gathering feedback here. So probably best to copy and paste and re-post your feedback about Forum issues on this thread here.
https://community.quickbase.com/discussions/quickbase-discussions/share-your-feedback-on-the-new-qrew-discussions/84096