Do, I need to resolve all the conflicts before proceeding to next cherry -pick
Yes, at least with the standard git setup. You cannot cherry-pick while there are conflicts.
Furthermore, in general conflicts get harder to resolve the more you have, so it's generally better to resolve them one by one.
That said, you can cherry-pick multiple commits at once, which would do what you are asking for. See e.g. How to cherry-pick multiple commits . This is useful if for example some commits undo earlier commits. Then you'd want to cherry-pick all in one go, so you don't have to resolve conflicts for changes that are undone by later commits.
Further, is it suggested to do cherry-pick or branch merge in this case?
Generally, if you want to keep a feature branch up to date with main development, you just merge master -> feature branch. The main advantage is that a later merge feature branch -> master will be much less painful.
Cherry-picking is only useful if you must exclude some changes in master from your feature branch. Still, this will be painful so I'd try to avoid it.