A beginner here. I want to give the same key frame to multiple meshes. Are there any other way than selecting every single one and giving key frames one by one?
Select to destination objects first, then the object with the animation. Then menu to Object -> Make Links -> Animation.
However, this will "overwrite" any other animation you may have put on the destination objects.
Then if you don't want the object to continue to share animation, use the Object -> Relations -> Single User -> Object Animation. This will make individual copies of the animation on each object, so you can further animate objects individually.
I can think of two ways: select all the objects you want to apply the animation to, then select the object whose keyframes you are copying last (to make sure that it is the active selected object) then press Ctrl-L to bring up the Link Menu. From there select "Animation Data", and all the objects you have selected should now have the same animation applied to them. Please note that if you have keyframed the active object's Location property that all of the selected objects will be moved to the same location as the active object.
If you don't want the other objects to match the location of the active object, but you do want them to "fly in formation" as it were, then select all your objects, again making sure the object whose animation you are copying is last, then press Ctrl-P for Parent, and select "Object (Keep Transform)" from the dropdown menu.