National Electrical Code Articles and Information

1. Yes, and the rules governing that are in 424.41(G).

2. They cannot be constructed of materials with thermal insulating properties [424.42]

3. You need at least six inches of lead length in the box [424.43(B)], same as when installing a receptacle in a box and for the same reason.

4. Yes, you can use EMT for this purpose. RMC, IMC, RNMC, and EMT are all approved methods [242.44(C)].
   
5. You must secure them per the manufacturer's instructions. If there are no instructions, the product is probably not identified as suitable for this application. Check to see if it is identified [424.45(A)] as suitable, and contact the manufacturer for instructions before completing the installation.