I'm going to be playing in a game using spheres of power. I'm looking to make a shifter focused on being a swarm and I have some questions.

General question:
If I start a transformation (or any sphere power that allows concentration to maintain) and initially maintain it through concentration can I spend a spell point to have it continue without concentration for the standard duration? If yes, does this cost an action?

Swarm questions:
I am confused as to what traits can be used to modify the swarm attack. Is this clarified somewhere or is there a list somewhere that specifies which traits are allowed?

Does the alteration sphere swarm trait grant swarm abilities that are not listed in the trait? Swarm traits that are not listed are being immune to critical hits (looks like this is replaced), being immune to flanking, being immune to spells that target a specific number of creatures, and half damage from slashing or piercing weapons.

Assuming I start as a medium size creature before transforming, do I gain the bonuses and penalties of becoming tiny sized? (basing off reduce person and the size alteration trait: +2 to attack rolls, +2 to AC, +8 to Stealth checks, +4 to Fly checks, -4 to Strength, +4 to Dexterity)

Am I allowed to use skills as a swarm? Does this depend on the transformation I apply the swarm trait to?

Thank you