Newb to POE2 (or POE) has support gem questions please

Hi. I am brand new to any of the POE games and have 2 support gem questions for POE2:

1) When a support gem says it supports "Attacks" does it merely support that individual skill or all player attacks (the tooltip seems to indicate the latter)?; and

2) Cold/Fire/Lightning Infusion - I have seen builds using 2 or 3 of these. Don't the negative modifiers just cancel the effects out and make the gems worthless?

Thanks in advance for the help!

1) a support gem changes how the skill works not your entire character.

2) same as your first question, would only be the case for the skill you socket them into and if you would stack them into the same skill for some reason. With the supports you mentioned the skill would still be able to do physical and chaos damage.