Try asking in the linked forum below if nobody here can offer sound advice. I think Most here are experts at GTA5, but not in driving in real bushes...
Nope. Maybe the easier roads. But not in the Delta itself. My in-laws and wife did that and had a Nissan Safari seriously kitted out back in the day. 4x4 or you will get stuck.
Depends where you going. Went fishing there 2 years ago and didn't engage 4x4. Drove to Sepupu camp, parked, camped, fished and drove back. But, if it rains and you go on any dirt road - you'll be stuck in 4x2.