Create IPsec VPN programmatically by android app

[Mob Acc]

I see IPSEC VPN api from android api 28 (android 9).
1. Is there any sample how to use it ?
2. Does it mean there is no IPSEC VPN api in older android versions?
3. Can I create IPSEC IKEv1 with client certificate with this interface ?
4. Can I create IPSEC IKEv2 with client certificate with this interface ?
Thanks a lot.