there is always a possibility but you should be ok.

Green Card for Parents!

yes he is eligible to file in behalf of his parents

Possible options to Migrating to Canada while on H1B in USA.

This is probably not the best forum. Most here practice US immigration law. You need to consult an attorney practicing Canadian immigration law.

Can I marry my boyfriend who has been in the US with a green card for over fifteen years?

The legal blemish could affect other immigration processes as well. Please consult an immigration attorney directly.

What is the next step in the immigration process after receiving the form I-797C?

What application/petition did you file?

Can I freelance to companies outside the US being a L2 visa?

You should be able to do that with the EAD.

I-130

It will be a separate petition, no need to do anything with the sisters petition. unfortunately saving of processing time is not possible.

Can dependent be on AOS, while primary maintains H1B?

Not necessary but is recommended to maintain non immigrant status until AoS is complete.

Which one to choose option a or b in part 2 application type in I-485 based on approved I-140 for the dependent spouse?

b. My spouse or parent...allows derivative status...

As a Canadian who has a job but does not plan on staying in the US for much longer, what type of Visa should I apply for?

It could certainly be a better option given the lottery situation.