Hello @Anonymous
For TextInput validation you can use IsMatch Function from this Link Here:
https://learn.microsoft.com/en-us/power-platform/power-fx/reference/function-ismatch
write the validation code on one errormassage label Like this
If(IsBlank(TextInput1.Text),"Enter Value in TextInput1",!IsMatch(TextInput1.Text, "[a-zA-Z0-9-]"),"Please Enter Proper Value in TextInput1")
and this code on visible property of errormassage label
If(IsBlank(TextInput1.Text) || !IsMatch(TextInput1.Text, "[a-zA-Z0-9 ]"),true,false)
To disable and enable the submit button write this code on Display Mode property of submit button
If(ErrorMsg.Visible,DisplayMode.Disable,DisplayMode.Edit)