To question 2):
Yes, MikroTik IS based on Linux.
The new web-proxy is developed from ground up by MikroTik, IIRC. But that has more or less nothing to do with the question if it's based on Linux?!
Best regards,
Christian Meis
ip route 192.168.10.0 255.255.255.252 192.168.10.253
/ip firewall nat add chain=dstnat in-interface=Internet protocol=tcp dst-port=3389 action=dst-nat to-addresses=x.x.x.x to-ports=3389
/tool torch ether1_public protocol=icmp