Transmission not working properly

More than likely these are not related issues so let's start with the reverse issue and we can work on the 4WD issue next.

The fact that you have to step on the accelerator and raise the RPMs just means you are increasing the pressure in the system so that the transmission will engage.

This is normally due to one of two issues. First the fluid is low or in poor condition so here is a guide that will help with checking the fluid:

https://www.2carpros.com/articles/how-to-check-and-add-transmission-fluid

While this process will work on most vehicles, this unit has an inspection plug so I attached that complete process below on how to check the fluid.

Next is the pump is not able to produce the proper amount of pressure to engage the vehicle in reverse. So, let's start with the fluid level because if the pressure is not correct then that means we need to rebuild the unit to find where the issue is.