One is migration I only got one srry
Initial conditions and chance play roles in the process of succession so if the ecosystem is in a good condition and chance is on it's side (no natural disasters or human interventions occur), succession can't happen because there is no destroyed area to build new upon.
I believe that hair and limbs are homology because all mammals have hair and similar limb structure. Hair loss and social behavior on the other hand are homolasy because not all mammals have them. Homology is the similar traits due to common ancestry while homoplasy is similar traits for other reasons other than common ancestry.
I believe it is muscle cells, I'm sorry if this is incorrect.