1) Fire and forget works like a MANPADS: you lock the seeker on target before the launch push launch button and then u can go away. Missile guides by itself. This is how work:
US Javelin
Israeli Spike MR
Japanese Type 01 LMAT
Chinese HJ-12
It also called LOBL (Lock-on Before Launch). You can't target a concealed target in this mode.
Spike MR ER NLOS in addition to fire and forget have fire and update mode, which allows switching targets in flight. Lock on target after launch (LOAL), it also allows u to chose the exact point of impact on locked target.
This is example of
fire and forget LOBL mode:
(Dots around the cross marker indicate that the target is locked).
This is Lock-On After Launch mode (0:38-052):
First it was flying manually towards a concealed target and then it locked on it (dots appear).
And here example of
switching targets:
Before the launch it was locked on one target and after it switched to another (which u could not see before launch).