Noob Question: Subraces

[Diaz Ex Machina]

So, I'm trying to create a bunch of subraces for my races. Somewhere in the forum I've read that this is better handled by the Alt. Racial Trt tab, so I'm using that, but I still need to understand some things:

• Can I change the ability modifiers of the subrace?
• Is it possible to add and remove available languages depending on the subrace?
• Can I change the random height/weight values for the subrace?
• Can I hide the single alternative racial traits from the Add Alternate Racial Traits menu in HL, leaving only the subraces available to choose from?

Thank you in advance for your help and time.