Question about button, icon-color and flipping cards

Hello,

I have different questions about different components. Would be great to get some help with this.

1.) What is the right was to set a route to a button? I tried something like this but this does not work.

<mdb-btn tag="a" to="/favourites" class="pl-2 pr-3" color="primary" icon="heart" rounded>Favoriten</mdb-btn>

2.) What is the right way to set the color for an icon? When I set an icon-color with color="secondary" it works, but not with color="grey darken-1". Why? And which colors can be set with color and which colors via class?

3.) How can I add a dynamic icon? I tried something like this but this does not works:

4.) My most important question: I want to display multiple rotating cards on one page (like rotating-card-example at https://mdbootstrap.com/plugins/vue/card-animations/#v-1). But these cards have dynamic content - so I can't set a fix height to the cards. What is the right way to solve this?

Thanks for some help!

Best regards,

Timo