No special access issues
1) No special rules, other than common courtesy and common sense.
2) From Bø, drive towards Lunde and take a right by a sign that says "Tveiten". Follow this road, and keep to the left where the road splits and asphalt ends. Drive along this gravel road and take a left and drive over the bridge when you reach the Uvdal lake. Continue on this gravel road, past the parking for Gygrestolen, and past the spectacular Uvdal Manor House (old large farm). Drive further on the road until there is a large space on the right side of the road, that is used for timber working. Park here, but make sure not to block any roads.
3) The approach on foot can be a bit tricky, as there is no continuous path leading to the main wall. Study the map and topology beforehand. Furthermore, the area has poor cellphone coverage, so that the gps on google maps / 27crags doesn't always work. The climbing walls of Tveiten are located in a narrow valley that lies south of the small mountain called "Styggedalsnuten". The main wall is located in the end of this valley.
After parking the car, continue walking straight ahead onto a lesser road. After ca. 450 meters, just after the road crosses a large creek, you must take a straight left onto an very old and overgrown lorry road. This road will take you to the valley. You can either walk inside the valley until you reach the main wall, or you can take the alternative route on the ridge south of the valley. The ridge is recommended, as the valley can be wet and slippery and is loaded with large boulders and dead trees.