You can use segmentation option available in VWO test settings to create a test that runs only on mobile devices. You can add a segmentation condition as shown below in image and include the desired mobile devices.
Upgrade your trial account directly to a paid account after your trial expires. No campaign data will be lost during the upgrade.
VWO does [A/B Testing] so disruptively, embarrassingly better than Google does that it puts a smile on my face.