R4-SF was built during the waning period of the Clone Wars. Like many of the R4 units of the time she was commissioned into service for the Jedi and like most, had her original head dome removed and the R2 dome style dome attached. This would be the first of many re-builts, though she was able to keep her green markings for most of her life.
During this time R4-SF served faithfully and was joined with a Jedi as his co-pilot. With her new partner she participated in many of the war's naval engagements and came to understand the values of freedom and duty. However, this stage wouldn't last very long and one fateful day her Jedi's ship was crippled. He was killed instantly and R4-SF was trapped in the fighter as it fell into the gravitational pull of the planet below. Luckily R4-SF was able to stabilise the ship enough for it's re-entry and was able to make a crash landing without being blown into bits. The R4 unit was able to make her way out of the crashed ship, but upon seeing her dead friend, R4-SF came to understand the sentient emotion of sorrow. She grabbed what she could from him as momentos and headed out into the badlands somewhat damaged and barely able to roll along.
It didn't take long for her to be picked up by a Besalisk garbage collector by the name of Yori Succondo who had been picking several days worth of debri from the battle looming overhead. Before R4-SF could react, she was roughly grabbed and thrown in the back of Yori's barge. Her damages became more severe with most of her head unit damaged and even her leg falling. All she could do was wonder what fate awaited her as she sat with the rest of the junk for several days on Yori's freighter.
Finally Yori came to a outer rim inhabited swamp planet. R4-SF was pulled out, cleaned up a bit and put on sale with some of the other "junk". As R4-SF looked at all the ruffians with her partial good eye, she thought she was going to be sold to the worst of them, when to her surprise a Mirialan family bought her. And as she travelled home with them she became even happier to find that they seemed very kind. The family consisted of a set of parents with two children, a boy and a girl who were already trying to to make friends with her, and a grumpy old grandfather.
When they arrived to their destination the father introduced R4-SF, who by this time had been nicknamed Suffy, to the other droids working at the vehicle repair shop. Most notably, this was when Suffy first met R3-DA, later known as Dango, a droid she would meet many times in her life's journey. Suffy was told that the previous R4 had fallen victim to a bad ion shock but that she would be repaired with the left over parts. The father was able to move SUffy's brain and memory modules and place them in the other R4's body, which was the smaller R4 design making Suffy a little bit smaller than her contemporaries, but she grew to love her new body.
Suffy enjoyed many days with her new family and co-workers, learning to fix a number of vehicles and small crafts. During this time her love of exploration began as she accompanied the family's children on a number of trips into the deep jungle. Because of the durability of the R4 line she was able to resist most environmental stresses like high humidity, mud, and water better than most of her contemporaries. She even learned other skills from the other droids, most notably R3-DA who had developed a large repertoire of secret talents. He mainly taught her how to rewrite her subroutines and create an area in her memory banks to resist a memory wipe. So like Dango she was able to avoid memory wipes and keep her personality intact over the years to come, even if her programming skill set changed.