There is no collusion; Flynn was wiretapped in December and unmasked by Obama administration, then lied in January and was cut loose by Trump in February. Marie Harf says of course they were wiretapping Flynn, he was speaking to Russians about undoing Obama policy and that was outrageous!
Certainly not a crime. The incoming President's security advisor has every right to discuss the new President's foreign policy objectives with any country. They could hark back to the Logan Act, but that has never been enforced.
Obama was talking to the Iranians before he took office.