feature.setStyle is not a function

The feature object retrieved by the map.forEachFeatureAtPixel seems not having the setStyle and get method

map.forEachFeatureAtPixel(e.pixel, function (feature) {
    boundarySelected = feature;
    feature.setStyle(highlightStyle);
    return true;
});
if (boundarySelected) {
    status.innerHTML = boundarySelected.get('name');
} else {
    status.innerHTML = ' ';
}

The setStyle method and get(‘name’) method should exist like shown in the Hover Example and in the Feature documentation

[MoonE]

The vector tiles are only rendered once and then cached, so changing the style of the feature afterwards will not work, plus you have the problem that the geometry may be split between multiple tiles and setting the style on just one of those features will give unexpected results.

When you look in the example in my previous comment you will find there is a separate layer created for highlighting the active geometry that uses the same source but renders with renderMode: 'vector', so no tile caching takes place. Using a style function and identifying the features by an id value will allow you to consistently style the entire geometry.

[MoonE]

Have a look at this example which is using a MVT source: https://openlayers.org/en/latest/examples/vector-tile-selection.html As written above the features of your tile source are not ol/Feature but ol/render/Feature which is a different class optimized for just rendering. They are not meant to be changed and there are a lot of functions not available compared to the normal ol/Feature objects.