Hi @Dmitry - each resort is different, and has different rules and protocols in place, so I would read between the lines carefully since improper usage could result in heavy fines and/or jail time.
Some resorts allow skinning up before the lifts start churning. Again, each resort is different so check into your favorite ski areas to see if this is allowed, which part of the ski area it's allowed in, and if there are any uphill passes or tags you need to carry. Most resorts that allow uphill in the morning require that you begin your descent before recreational skiers start using the lifts to diminish crashes and accidents.
As far as accessing side country to get to the resort, again read between the lines for each resort's rules and regulations, but I'm going to guess most will say this is a "no-no." Also remember that the side country is not maintained, so please make sure you are prepared with your beacon, probe and shovel, plus your avalanche awareness education and understanding of current avalanche forecasts . And do not go alone!
Be safe, whatever you decide to do!