Normally yes at least they remove old signatures...
Better to move this to Host Intrusion Prevention forum
Yes, it will have all previous signature details.
Yes, you will have all previous IPS Content, however, be aware that some signatures require specific HIPS builds to apply. Read the signature description; it will mention the details (e.g., this signature requires HIPS 8.0 Patch 2 or higher; this signature requires HIPS 8.0 Patch 4+, etc.).