A: Yes. Keep both sounds_english.dat and sounds_german.dat in the same folder. Then edit LocalSettings.ini to switch languages by changing the Language= line.
If you purchased Hitman Absolution on Steam, you can download the English language pack directly from the Steam client. Here's how: Hitman Absolution English Language Files Download
A: Hitman: Absolution features full voice acting for every NPC, mission briefings, Agent 47’s internal monologue (voiced by David Bateson), and environmental dialogue. Compressed, 1.2GB is standard for a AAA game of that era. A: Yes