1. We can use across or over to talk over a position on the other side of a bridge, road, border, river, etc.
- Once she knew she was across/over the boarder, she knew she would be safe.
- They came towards us across/over the bridge.
- I pushed the plate across/over the table to her.
2. Use over rather than across when we talk about reaching the other side of something that is high, or higher than it is wide.
- The animal jumped over the hedge.
- It is difficult to go over the top of the mountain.
3. We use across rather than over for things we think of as flat surface or an area such as a country or a sea.
- He traveled across the country to find her.
- Airtel broadcasts its channels across the Indian subcontinent
4. When we talk about following a line or some kind, we use along
- The trees were planted along Majeedhee Magu
- We had to walk along a narrow lane when we went to his farm
5. We use through to emphasize that we are talking about movement in a three dimensional space, with things all around, rather than two dimensional space, a flat surface or area.
- We walked through the trees to look for the herbs
- He pushed his way through the crowd of people to get to her