Google earth engine javascript

I need help finishing my javascript for albedo calculation in Google Earth Engine. I have a script already that loads all Surface Reflectance products of Landsat 4-8 in Google Earth Engine and does cloud masking and cloud shadowing. I need help finishing the script, specifically: 1. How to clip my images (collections) to the area. Polygon in the form of a fusion table (ft) is already in the script. I just need a code to extract images according that polygon boundary. 2. Then I need help in selecting specific bands in the collections. For example Landsat 4-7 collections need bands B1,B3, B4,B5, B7 and Landsat 8 needs bands B2, B4, B5, B6, B7 and to use these in my albedo formula. 3. Lastly I need to be able to export these images in the form of a geoTif file. I will provide my Google Earth Engine log in info so you can work directly on my script. Thank you