Advanced form styling 1 skill test : https://codepen.io/strofa/pen/abaRedr
Advanced form styling 2 skill test: https://codepen.io/strofa/pen/dyqgxMo
Advanced form styling 3 skill test: https://codepen.io/strofa/pen/XWPxvGW
Advanced form styling 1 skill test : https://codepen.io/strofa/pen/abaRedr
Advanced form styling 2 skill test: https://codepen.io/strofa/pen/dyqgxMo
Advanced form styling 3 skill test: https://codepen.io/strofa/pen/XWPxvGW
Hi @Strofa and welcome to the community 
Nice work! 
Here are some comments:
Mostly correct. When using prefixed and unprefixed versions of a property (e. g. -webkit-appearance: none; and appearance: none;), the unprefixed version should always come last. Reason: When browsers implement the unprefixed version, it will overwrite the old unprefixed one.<img> tag you could also use a background image on the <div>. background: url(search-24px.png) no-repeat center; (with some size adjustments).
Correct.
Correct.I hope that helps. 
Have a nice day,
Michael