Neither 898 has Auto Chart Live. You need at least an ONIX, SOLIX, or Helix to have that feature.
1. For contour mapping it uses 2D sonar for depth and GPS for location. Depth comes from the center of the sonar pulse.
2. Yes as long as you have it turned on.
3. Yes all data is blended.
4. To use it in other units, you need another unit that has Auto Chart Live and the data is transferred to a Zero Line Card memory card ONLY.
5. The route you take makes no difference except what is beneath the transducer is the only accurate part of any produced contour lines. The rest is fake (interpolated).
This is two tracks beside each other done with my Helix 12 SI GPS, note how wide the software makes the contours for a single path. All that to the sides is fake. All computer generated contour mapping does the same thing. Even the USGS map data is collected in intervals and contours are manually filled between data points (interpolated=fake).
You can use Recordings with your unit and process them with the computer software Auto Chart or Auto Chart Pro. Copy the created contour mapping to a Zero Line card, then the data is read as Lakemaster mapping by any unit that can read Lakemaster mapping.
I have Auto Chart Live contours on a single Zero Line Card that I did with my ONIX, SOLIX, Helix 5 DI GPS G2, Helix 7 SI GPS G2, and Helix 12 SI GPS.