IPsec tunnel limitation on SRX high end with JUNOS 12.1

Hi Dear all, I need to do GRE over IPsec on SRX5800 with JUNOS12.1. (1) Is it supported? If not, which JUNOS version supports it? (2) Any limitation with IPsec or GRE or GRE over IPsec? I know that it should be route-based VPN. And GRE endpoint should be different from IPsec endpoint. Anything else? Thanks! BR/ Claire