Some weapons require one hand to wield, and others require two. A few items, such as a longbow, list 1+ for its Hands entry. You can hold a weapon with a 1+ entry in one hand, but the process of shooting it requires using a second to retrieve, nock, and loose an arrow. This means
you can do things with your free hand while holding the bow without changing your grip, but the other hand must be free when you shoot. To properly wield a 1+ weapon,you must hold it in one hand and also have hand free.
2. No, while you could release one hand from the weapon(release action page 470) as a free action, but adding a hand would cost you an action (interact page 470)...look at table 6-2 table 273.
Detach a shield or item strapped to you 1 Interact
Change your grip by removing a hand from an item 2 Release
Change your grip by adding a hand to an item 2 Interact
That is how I read it
Somantic specifically says "You can use this component while holding something in your hand." Compare that to material components which say you must have a free hand. Sounds like it would work with both a bow and a two-handed sword.
Being pointed out the info about somatic and the original questions limitations, I totally agree. You could still use a greatsword because you would never need to release your weapon for the spell. Any weapon for that matter unless it was a material component spell that was not covered by eschew or the feat was not known.