I am facing a problem when changing the size of labels. The html codes are appearing in my fields.
please stay tuned for the next update to the Survey123 app. This update is planned for around mid April 2016 and will include a new app setting to easily change the font size. Additionally, you will be able to use Survey123 Connect to set the font size with HTML syntax as you describe, but unlike in previous versions, the upcoming update will drop the HTML from your field aliases.
Upcoming update will be announced at:
At the time of writing, label size is not a configurable parameter.
We set the font size for choices and responses to a value that is readable in phones, tablets and desktops... but this value is not configurable. This is a good enhancement request. Lets see what others think about it.
Recommend raising this on ArcGIS Ideas and subscribing to the enhancement on the Survey123 Github repository. Should also point out that they have open sourced the code for Survey123 with the 1.1 release of AppStudio, so potentially could DIY.