When setting BorderBrush, BorderThickess, FocusedBorderBrush and FocusedBorderThickness do not apply on the entire entry control, they apply only on bottom.
<VerticalStackLayout>
<telerik:RadEntry Text="Hello World" TextColor="DarkRed"
Background="Wheat"
FocusedBorderBrush="Yellow"
FocusedBorderThickness="10"
x:Name="entry"
BorderBrush="DarkRed"
BorderThickness="8"
CornerRadius="5,7,7,5"
WidthRequest="150"/>
</VerticalStackLayout>
And the result:
Place the entry in a RadBorder:
<telerik:RadBorder BorderColor="Red"
CornerRadius="5,7,7,5"
BorderThickness="4,4,4,4">
<telerik:RadEntry Text="Hello World"
TextColor="DarkRed"
Background="Wheat"
x:Name="entry" />
</telerik:RadBorder>