Hello,
1) Contact your hosting provider to fix the mentioned errors. I suppose server configuration causes issue with the slider plugin, not our theme and we can do nothing with this. So, ask them to check the errors and fix all the necessary limits to allow the Revolution slider to show the preview https://prnt.sc/x7mmfb
2) Choose the layer > click on Visibility > choose where you want to show this layer https://prnt.sc/x7mt32 For which layer does this option not work?
Regards