Had this thing lying around. Obviously not playtested.
The skills available to the character vary based on their age. The skills that were present at any given point in a character's life (divided into four year terms) should be noted down. A character whose age has been reduced must make an EDU check to use their normal allotment of skills. A success indicates that the character can act normally. A failure indicates that they must use the skills they had at that time in life. A character whose age is reduced below 18 (or whatever age they started careers at) does not suffer additional penalties to their skill ranks, but can only make use of whatever commonsense talents they had at that time (i.e., effectively untrained in all but background skills). Further, a character reduced past maturity also begins to suffer physical DM penalties, similar to the ones suffered for advanced age. This is related in a later section.
Note that characters whose age is in between a term block (four year period) don't have their skills affected. Only those that are pushed into a previous term's experience suffer penalties. Example: Riordan, a Scout Veteran investigating some ancient ruins, attacks an alien bot right by the entrance. He uses a synth cudgel for this attack. He is age 30, and has Melee 3. He easily makes the roll and makes good progress on the brawl. Later, after suffering from some malfunctioning nanotech in the alien facility, Riordan has found himself reduced to the age of 22. At that age, Riordan had only acquired Melee 1. He makes an EDU check (with an EDU of 7, he has no bonus or penalty to the roll). He rolls a 6 and fails. The scout's head fogs up for a moment as he sneaks behind some malfunctioning service droid. He only has Melee 1 for this attack, effectively.
Some skills are more important to a character than others. This is known as a core skill. A core skill cannot be reduced below 1 by regression. The player should consult the referee as to what abilities the PC predicates much of their values on. A character will probably have 1-3 core skills.
After a few more scuffles in the facility, Riordan finds himself back at age 18. Though he sometimes struggles to remember the things he learned in his career, his memory of Navigation is as strong as ever. He's always been an explorer at heart, after all. Taking refuge in an old storage room, the young scout finds himself rather expertly drawing a map of the facility thus far (Navigation-1, roll of 7+1=8).
Similar to elderly characters, youthful characters also suffer aging penalties. This stems from a lack of development. Each penalty is effectively applied over the character's existing attributes, the characteristic and not the modifier is affected. The original attribute still exists as potential. If the character is restored to maturity (artificially or otherwise...) the attribute returns to it's original value. The details for each age category can be seen below.
A character's attributes cannot be reduced below 1 by youth penalties. Take note that these scores reflect a lack of development rather than ill health, as in most cases.
Character's with active Psi values are still treated as trained even if they are regressed to a point before they learned their psi skills. However, they cannot access said psi skills beyond the preservation provided by core skills.
Example: After receiving a very strange distress call from his friend, Psion Deryll exits the ship to investigate the ruins Riordan said he would check out. Deryll is quickly reduced in age by the strange technology of what is now revealed as a precursor's nursery. Deryll, now aged 6, attempts to outrun a nanny bot. Though a decently healthy fellow normally (END 7) Deryll finds himself running out of breath faster now (END 3, -4 from Young Child Category). He gets a good start but soon slows down from exhaustion (roll of 8-1= 7). He soon finds himself scooped up by the nanny bot. Fighting back the urge to cry, Deryll simply pouts and stares off as the nanny bot coos on the journey. A grin grows on his face as he realizes he can do what would normally be against the rules. Deryll uses Telepathy, the skill he was most eager to learn his whole life. It is a core skill and is thus valued at 1 despite his young age. He succeeds (roll of 7+1) and soon probes the bot's synthetic psyche. It appears like the bot is eager to take him to a playroom, having given up searching for Riordan in the southern corridors of the complex. That'll be useful to know if he can actually get out of the robot's arms...