A 190
Metamagic is applied when a spell is cast. If a Master Transmografist casts Shapechange to turn into one of its favored shapes, the spell would gain the benefits of the Extend, Still, and Silent Spell feats. However, If a Master Transmografist casts Shapechange to turn into something that is not a favored shape, the spell would be cast normally. Any subsequent changes of form, whether from the normal function of Shapechange or from the Warshaper's Multimorph ability, will have no metamagic effect on the spell.

A 208
Hideous Blow will not provoke attacks of opportunity unless it is used with a weapon that would normally do so, such as a whip.

A 209
As a full-round action, the Warlock can make one attack against an opponent's regular AC. If the attack hits, it deals normal suglin damage plus Eldritch Blast damage.

A 210
Sometimes. You need to look at the individual monster entries to be sure. For instance, soulfire will protect against a shadow's strength damage, because that is listed as a negative energy effect. A vampire's blood drain does not have that language though, so soulfire will not protect against its constitution drain.