1. What is does your best friend look like? - What does your best friend look like? - два вспомогательных глагола не могут стоять в одном предложении, и так как есть основной глагол, оставляем does; 2. The garden is in front of to the house. - The garden is in front of the house. - всегда используется in front of N; 3. My sister likes to sailing a boat. - My sister likes sailing a boat. - после глагол like могут употребляться либо to V, либо Ving; 4. My school is behind of my house. - My school is behind my house. - всегда используется behind N.
