Not without their consent - and if you do you risk injury to yourself, them and anyone else helping. Wheelchairs understandably vary in weight, but including the person in them can come in at over 200kg. That isn't a safe weight to lift.
Yes, there are. Isn't it outrageous, 22 years after the law on reasonable adjustments to goods and services, that so many places don't have level access?
Actually, it does. The equality act applies to all service providers, and that means anyone selling things to the public - be that goods or services.