Hong Kong Museum of Coastal Defence is the farthest one from your hostel. Museums of Art and Space can be reached by walking from Exit E of Tsim Sha Tsui MTR station and Musuems of History and Sceice can be reached by walking from Exit B2 of Tsim Sha Tsui. Heritage Museum is 5 minutes walking from Che Kong Temple. Mongkok is in the middle of Heritage museum and those in Tsim Sha Tsui. Museum of Coastal Defence is far in the west costal area of HK Island, nearby Chau Kei Wan mtr station. As to others, by mtr or bus. As to a round trip, I don't think you can finish them in one day. You can take mtr from Mongkok to tsim Sha Tsui, then use the same line to Admiralty and change to HK Island Line to Chau Kei Wan. As to Heritage Museum: bus is better. You can take bus 170 at Pui Ching Road to Sha Tin and then walk 15 minutes to the museum.