To whom should I ask permission if I want to use a figure from a paper published in ResearchGate? Do I need to ask permission from ResearchGate or the Author?
ResearchGate is just something like a storage, it is not a publisher. Copyright for papers stored here is not transferred to Researchgate. Permission to use a figure can only be given by the copyright holder, e.g. the author(s) or in most cases the publisher. You may asked one of the authors the question who is the copyright owner.