I can install the config from RB951G-2HnD go to RB3011UiAS-RM ?
You probably could but you may need to rename or remap interfaces and adjust firewall rules etc.
Also the RB3011 does not have a wireless card.
not directly and not with backup.
you will have to export config files, check each line and then import to the new device.
the two devices should ideally be on the same firmware version as well.