0 past simple and past participle of open
2 to move something to a position that is not closed, or to make something change to a position that is not closed:
3 If a shop or office opens at a particular time of day, it starts to do business at that time:
4 to make something available:
We can complete it step by step however long the road is and it can't be completed however short the road is if you don't even mark your footprint.