I’ll answer Question 2 first.
Yes you can set up a layer 2 PepVPN that transparently extends a subnet/VLAN from one Peplink device to another remote site. The device at the remote site to all intents and purposes becomes a transparent remote switch attached to the core location. Setting up a Layer 2 PepVPN Profile in Firmware 6.2 Onwards
Question 1
The answer is yes - with a caveat. You could add a layer 2 VPN between site 1 and 2, linking a vlan on site 2 with the main subnet/vlan on site 1. Then you could have a device on site 2 with an IP address from site 1. That device would route all of its traffic out over VPN back to site 1 and out to the internet from site 1. The caveat is that if this device on site 2 connected over L2 VPN to site 1 wanted to route traffic to devices physically next to it on site 2, that traffic would be sent over the layer 2 VPN to site 1 and then back over the other layer 3 VPN tunnel to site2.
It might be worth explaining what the requirement is in more detail as there is likely a less complicated way to achieve what you need. What is the device on site 2 that needs an IP in site 1’s subnet?