The main differences between the RA-434 and RA-535:
RA-535 has a shorter reset
RA-535 included KNS Anti Rotation Pins instead of Anti Walk Pins
RA-535 has a Nickel Teflon coating on the hammer and silver blade version.
Yes, this will work in a Spikes Tactical AR9.
Yes, provided that the trigger pin hole diameter on the lower receiver is .154
Yes, this trigger is compatible
Yes this will fit the JTE AR15
Yes, this trigger is compatible with all milspec style lowers as long as the trigger pocket is milspec dimensions.
This trigger will fit any milspec trigger pocket. Most AR10/DPMS style 308's utilize a milspec trigger pocket.