I’m not precisely sure what you’re asking. Could you be more specific – perhaps give an example?

Which specific reaction with NBS?

Probably. Especially if acid catalysis is used. https://pubs.acs.org/doi/10.1021/ol006952r

Please answer

Yes, it will oxidize primary alcohols to aldehydes in polar solvents through forming a hypobromite intermediate. Interestingly, NBS is more selective for secondary over primary alcohols, and also very selective for oxidation of axial (vs equatorial) groups in steroid systems. See Chem. Rev. 1963, vol 63 page 21. https://pubs.acs.org/doi/10.1021/cr60221a002

Possibly. I’m aware of N-chloro dialkylamines doing bridgehead chlorinations, see J. Am. Chem. Soc.1974 96 134307-4311 . https://pubs.acs.org/doi/10.1021/ja00820a042

That will likely be an allylic bromination.