1. It depends if any of the endorsing bodies will endorse you based on your idea/business etc.
2. You can apply for any visa you qualify for at any time. Not sure what you mean by your visas rejected (specially tier 2 gen) comment??
3. You can apply for any visa you qualify for. Note that your partner cannot switch to Tier 2 General from Tier 2 ICT without 12 months cooling off period.
4. Only you can decide which option is best for you based on your circumstances. Note the innovator visa is very new, so many won't be able to comment on which is better. Visa fees for innovator visa are more than Tier 2 general.
5. I already answered this in your other topic (now merged with this last post), that you need 5 years on innovator visa. Note is is also not a like for like replacement visa for tier 1 entrepreneur. Innovator visa is not a points based system visa. Innovator visa requires 5 years residence for ILR.
5 year is little challenging as we will have to make all the investments for visa / IHS/ etc and this will be twice for innovation visa
There is no shortcut route to ILR. You require 5 year residence.