1. Is 922 is better than 722 + slingbox because the remote 922 viewer can similataneously see channel X on laptop and his family can see channel Y at home (not possible with 722)?
I don't know if its better, since the primary difference is that the second tuner meant for a second relocation is tied to the embedded Slingbox.
2. Buying 922 means Dish tech can come for home visit for installation and problems. Sling support is only on phone, and free only for 90d. Dish tech supprt is only $6 per month + $15 per visit. Is this a big factor in favor of 922?
Maybe? Your results will vary on personal experience.
3. Is the best advantage of 722 that by running a coaxial cable can get Dish in 2 rooms? Not an advantage for me since I do not want a wire to go from one room to another.
Again, it depends on how you expect to use it. It's not that one is better than the other, but the 922 model gives you different option.
4. Will the Dish tech know enough about installing 922 since still new? Is 722 less likely to be a problem since Sling techs are more experienced?
They should but it'll always vary on the individual installer. They have access to their central office too, so they can always ask them questions that they don't know.