For a healthy green lawn you should have it mowed and maintain it on a weekly basis to ensure proper growth height. Grass to high can act as a barrier for nutrients and water trying to get into the root system. Lawns cut to low can lead to access burning.
To maintain a green lawn all year your irrigation system should be set to water daily at minimum of 10-15 minutes per zone depending on water pressure, water early morning and early night daily.
Signing up for a fertilizer program with a local lawn care company to maintain your lawn yearly is a smarter and better investment than going to a big box store and trying to figure it out yourself.
A proper base for a paver walkway should have a minimum of 8" processed stone ( preferably 12" ) compacted in 2-3" lifts with a plate compactor with over 4000lbs of force.
A retaining wall or set of custom built steps built in place in New England should have a properly built footing installed below the frostline to reduce heaving throughout the freezing and thawing process.
All bricks and pavers shall be layed on a 1" bed of sand. While some contractors use Stone dust paver manufacturers will not warranty products laid down on stone dust.