Pg 129 SR5
Skill group advancement uses special rules. If you want to advance one skill from the group without advancing the rest, the skill group is broken and you get each of the skills in the group at the former group rating; then you can increase one of the skills. If you want to get the skill group back (or get a new one), you must first get all of the skills in the group to the same rating.
Pg 88 SR5
When a skill group is purchased, the character is considered to have all the individual skills of the skill group at the rating of the group. the character wishes to break up the skill group during game play and raise only one of the skills, he is free to do so, but may not raise those skills as a skill group again until all skills possess the same rating. Skill group points may not be used to purchase individual skills and vice versa. In addition, skill groups cannot be broken up in this step, so individual skill points cannot raise the ratings of skills purchased as a group. (Note that skill groups can be broken up in Step Seven: Spend Your Left Over Karma (p. 98).
Pg 89 SR5
Specializations cannot be purchased for skill groups. Skill groups reflect a general understanding of similar skills rather than a particular expertise that a specialization denotes. Players may choose to buy a specialization for an individual skill within a skill group, but if they do so the skill group is broken from that point forward, meaning that all skills of the group must be raised separately. Additionally, once a specialization is taken for a skill in the skill group, it is impossible to reconstruct that skill group. This cannot happen in Step Five of character creation— you can only break up a skill group by buying a specialization for it in Step Seven (see p. 98 for details)
Pg 130 SR5
Specializations are not allowed for skill groups.