2) Was that 4% grade always part of the railroad of old times?
"The mountain" is 2-3%.
At the "Top of the Mountain", there was a stub end siding for doubling the hill. For today's operations, the siding was extended slightly and a crossover switch was added to allow for run-arounds. It makes for a good talking point as it serves as the current end of public operations. Public trains will not begin down the mountain until 2021.
Note that this is not really any sort of mountain. It is just a long grade; "The Mountain" and "Top of the Mountain" were the designations given during the railroad's initial operations.
3) Did the railroad have braking of some sort when in operation or was it non braked?
The WW&F (as did other two-footers) employed straight vacuum brakes on some trains/cars in later years of operations. The restored WW&F is taking that operational detail to the next logical step by designing and installing the Eames Automatic Vacuum Brake system. The automatic system was patented by Eames, but was never implemented due to his unfortunate demise (linked to his rival, George Westinghouse.) The design and implementation of this project was funded, in part, by a grant from the National Railway Historical Society.