Can you please edit your question using Tip on formatting code in posts here? How to ask a good question
It’s also helpful to share a clone link to your app.
1 and 3: You have Form1 set as your startup module. That means it controls the flow when your app starts. If you want to call a function from Module1, you’d probably call that function from Form1 somehow. When you call that function, you can pass the Form (that is, “self,” if you’re calling the Module1 function from within a a Form1 method) to the function as a parameter. Then you can access anything from Form1 that way. Another way to access a form is the get_open_form() function. (See Anvil Docs | Navigation)
2. To trigger an alert, though, you don’t need get_open_form(). TextBox() is not a method of your form. It’s a class that typically gets imported to form code via the “from anvil import *” line.