Why my old tablet doesn't support some css lin

I try to make a hybrid app (using PhoneGap) but my main problem is that so far i looks different on every platform. I the browser on PC and on the Android 5.0+ looks as I want to but on older versions of android appear some problems. I've tested it on a 2 different tablets. Both with Android 4.2.2.(Samsung and Lenovo). Both of them don't recognize font unit vw (vh neither). One on them doesn't recognize commend "border-radius" or at least irregularly: photo. Whereas the second one has some troubles with animations e.g. like this one:

.totheleft{
animation-name: nalewotrzy;
animation-duration: 1.5s;
}

@keyframes totheleft{
to {transform: translate(-100%, 0%);}
}

And now I don't know if maybe the old versions of Android don't support CSS3 or I implemented my css file incorrectly into html code:

<head>
<link rel="stylesheet" href="index.css"/>
</head>

I'm quite new in programming.

Until Android 5.0 Lollipop the WebView in each device is part of the Operating System image. Unfortunately this means that unless the OS is updated that HTML5 features/bugs are frozen in time.

With Android 5.0 the WebView is now based on a Google Play updated component called Android System WebView.

See: https://developer.chrome.com/multidevice/webview/overview

Alternatively you could use the CrossWalk Project: https://crosswalk-project.org/ as your WebView for a more consistent experience on old Android versions (4.1 and higher) but at the cost of making your app bigger due to adding in its own WebView.

See: https://crosswalk-project.org/documentation/about/faq.html#Distributing-Crosswalk-Project-applications and 71mb added to app size for crosswalk