This Thesis presents experimental results of quantum transport measurements on high quality (HQ) suspended graphene devices. A high-precision transfer technique for graphene flakes was developed and used to fabricate a suspended HQ graphene device with additional bottom gate structure. The behavior of such device is consistent with the presence of a pn junction, and electronic transport occurs in ballistic regime over a length of 1 micron. As compared to the previously measured devices, the ones produced by this technique show one order of magnitude longer ballistic transport. Using the developed method, HQ tetralayer graphene (4LG) multiterminal devices were fabricated, their quality confirmed by early onset of Quantum Hall Effect. At low temperature, 4LG shows thermally activated insulating behavior around charge neutrality. Based on similarity of 4LG with insulating bilayers, staggered exchange potential mechanism of interaction-induced insulating state is proposed. Even-odd effect of interactions in graphene multilayers is suggested.