Hi @Ruben26 ,
1- Yes, you can retrieve information through a button click. When you're working with Power Pages it supports client-side scripting. There are couple of ways you can either bind it using jQuery or you can also use JavaScript for that. It depends how you want to make it done.
2- I'm unsure, if there is any OOB way available to do this but other option that came to my mind is you can bind date selection with a custom validation where you can validate if user select weekend, you can show an alert message on screen and enforce user to select something else. But I would recommend having a look into Code Component Framework as well and you can design your custom widget as well.
3- If you want to have your own custom login page that is supported in Power Pages Site, and you can design it according to your needs. Here is one example how to do that. Custom Login Page | Power Pages
Thanks,
Saud
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