If I install opera is it automatically added VPN, and what ISP can see through opera VPN. I am using wireless connection. Can data be see on my router?
Regular Opera (Opera One) and Opera GX on desktop for example have a built-in VPN when used in most countries (but not all). It’s disabled by default. When enabled, traffic in Opera travels encrypted through Opera’s https proxy servers in/out the other end from/to sites. Goto the URL opera://settings/vpn to control when to not use the VPN for certain cases.
You would have to test to see if Opera incorrectly doesn’t use the VPN for a connection in Opera or if it leaks any info (to your router or sites) about site traffic running through the proxy. You can try DNS leak and VPN leak testing sites to see what you come up with.