Hi @cseducator_mindchamp, thanks for asking these questions. The answer to most all of this likely lies in the fact that your app is using a webviewer and some of the default SDKs (software development kits) that all Thunkable apps inherently contain will not allow you to publish an app on the play store solely targeting children.
Using a webviewer, depending on the site(s) visited, those sites may collect and/or store data about the users visiting and this is what Google has flagged. There is no way to avoid this, even if the site(s) coded into your app are child friendly. Unfortunately, Google does tend to check and flag issues asynchronously–your app may be flagged after publication as well on a later version.
Because your app has a webviewer being generally used, your data safety form must include in your data safety form for publishing that your app does collect or share any of the required user data types and specifically Device or other IDs.