On the web form, questions that are select_one, set to minimal appearance and also read only are still interactive to the user. This is very confusing for the users as it accepts their change in the drop down but the change won't be saved. I have found some workarounds using text, notes, jr:choice_name etc... but these are very time consuming to implement. There is also a major issue that if that question is also set to 'required', on ios one of the options in the drop down is '....' (null basically) this will make the form unusable if this option is selected as they are not meeting the required status and it wont accept any other values now. Baiscally these form elements should not be interactive if read only. I think the date selector is the same plus others no doubt. It would be good to see this fixed. Using latest version, connect etc... but has been a problem for a while.
Regarding the issue you reported here:
1. Interactive dropdown list for read-only with Select_one question
>This is a valid issue with web form. I encourage you to submit this issue as a bug via Esri Support. Our Support team will assign an official bug number for your records. This number can be used to search for and subscribe to the bug on the Esri Support site. If the issue is reported by other customers it will be attached to the same bug report, which helps us assess the impact of the issue and prioritize it accordingly.
2. The ... option on iOS phone
>We have an internal issue logged for this on our backlog list. I also encourage you submit this as another separated issue to Esri Support so that this issue can be prioritized for a future fix.