Phoenix Claw acts like a Scape Doll and will revive you if you die with it equipped and then gets deleted. This is not a bug.
Some of the rooms in Seabed have areas where you can't hit enemies. Something to do with the walls' hitboxes I think. Would be nice if this could be fixed.
H/battle, v101 and Blue Odoshi Violet Nimaidou (and possibly some other items that I can't remember) have the highest attack speed boost of 40%.
Attack speed never stacks.
AFAIK it was never possible to get Photon Spheres as a reward from Beach Laughter in Blue Burst. The reward for completing the Heart system was changed to Type-M weapons.
The item you equip will be the one that determines the stats of the resulting item.
example:
You have 50h Milla and 0h Guld. You equip the Milla and 'use' the Guld on it. Result is 50h Guld Milla.
You can also get item rewards from gov quests. Most of them are crap but there's a couple decent ones such as the 40h Vjaya, 50h Double Saber and 25h DoB.
http://www.pso-world.com/sections.php?op=viewarticle&artid=2426