You could... You'd be an asshole and the GM might start calling on checks to have you back up that swagger you shouldn't have. Not really any different than trying to get away with picking a troll off the ground with STR/body 1.
Some game designers think that logic, intelligence, or cha shouldn't be game stats because they aren't able to be role played well (you don't become a genius because your character is, nor do you become less socially ackward for having a high cha).
Security tactics is often seen as a skill. Knowledge skills also aren't drawn from a set list.
Yes, but you can easily roleplay more stupid than you really are. And if the team does not know what to do, a gm can give a hint to the player, whose character's intelligence is the highest. And so on. At least you can simulate higher intelligent. The result is not maybe a perfect, but should it really be?
Some game designers may think that way, but in Shadowrun your characters have cha, int and log. And because they have those attributes, what it matters, what some designers think?
With a good security tactics you know what generally the security workers do, but it does not never give you a knowledge what is behind the next door in an unknown building. And in combat situations the gm can give you dice pool benefits if you have security tactics knowledge. Simililarly as small unit tactics can give bonuses.
But these are only opinions. You can do as you want because of fun. It's completely ok for me if you play differently.
